New Super Mario Bros. Wii/Enemies

Goombas

 * Goomba: Denizens of the Mushroom Kingdom who have turned traitor and now serve the Koopa Troop. They can be flattened with a single stomp or defeated in all sorts of ways.
 * Paragoomba: A Goomba with wings, essentially. Stomping it grounds the Goomba, which can then be dealt with as above.
 * Micro Goomba: Tiny Goombas that can appear in a few worlds. These can't hurt you, but if they get onto you, they can crawl all over you and slow you down. If that happens, Spin Jump to shake them off.
 * Grand Goomba: A large Goomba twice the normal size. Normally seen in the World 1 enemy ambush. Stomping one causes it to split into two regular-sized Goombas.
 * Mega Goomba: As if Grand Goombas weren't big enough, these huge critters are four times the normal size and split into two Grand Goombas when stomped.

Koopa Troopas

 * Green Koopa Troopa: The rank and file of the Koopa Troop, these turtles will walk the levels, turning when they hit a wall or other enemy but walking off ledges. Stomping them once causes them to retreat into their shells, which you can pick up and/or kick along the ground. A koopa shell can defeat other enemies as they slide along the ground but can also hit you, too!
 * Red Koopa Troopa: Unlike their green counterparts, Red Koopa Troopas patrol smaller areas because they turn around at a ledge. Otherwise, they act the same.
 * Green Koopa Paratroopa
 * Red Koopa Paratroopa: Koopa Troopas with wings that let them fly. They can be seen flying either in back-and-forth patrol paths or simply moving along in a certain direction. Stomp them once and they'll be grounded, reverting to the walking patterns dictated by their shells.

Piranha Plants

 * Piranha Plant: Carnivorous plants that were once confined to living in pipes but can now be found all over the place, chomping for Mario. Many of the ones still in pipes can sense when Mario is nearby and won't come out if he's too close. Be careful otherwise.
 * Venus Fire Trap: These more-aggressive plants have the ability to spit fireballs in your direction when they come out.
 * Super Piranha Plant: Freed from the confines of the pipes, some Piranha Plants have grown to gigantic proportions such that it takes three fireballs to wilt them, but defeating the big plant is usually worth it, as they usually leave behind a bounty of coins.
 * Super Venus Fire Trap: A big Piranha Plant that can both give and take fire. Like the chomping version, it takes three fireballs to beat this guy, and he's spitting fireballs of his own all the while.
 * Stalking Piranha Plant
 * River Piranha Plant
 * Muncher: Small but unstoppable, these plants can make going difficult. You can't remove them without help from a P-Switch; you usually have to find ways around them. Treat them like spikes.

Hammer Bros.

 * Hammer Bro: These elite members of the Koopa Troop toss a never-ending supply of hammers your way and have a tendency to jump up and down if there are platforms in the area. They can be stomped and dealt with otherwise but the constant barrage makes approaching them difficult.
 * Boomerang Bro: Hammer's relatives from down under, instead of hammers, these green Bros toss boomerangs. They're slower and more predictable than the hammers, but remember: boomerangs come back!
 * Fire Bro: From the hot desert, these red Bros lived on Fire Flowers and gained the ability to spit fireballs at you. These act just like Mario's fireballs when launched.
 * Sledge Bro: This Giant Bro tosses hammers like the regular Bro but is so huge that when he leap, he causes earthquakes upon landing, stunning you if you're on the ground.
 * Ice Bro: The newest Bros from the frozen reaches where Ice Flowers are their preferred diet, meaning they attack by spitting ice balls. Just like with your ice balls, not only will they hurt you, but they'll freeze you in ice momentarily.

Beetles

 * Buzzy Beetle: These critters may wander a level in the same way as a Green Koopa Troopa. You can stomp, carry, and kick them like Koopa Troopas, but their special shells mean they don't react to fireballs, but they will react to other things. Also remember that Buzzies can sometimes be seen crawling on ceilings. If you see one like this, they will drop from the ceiling and spin towards you when you get close.
 * Spiny: The annoying spiked-shell critters that are constantly thrown by Lakitu. Their spikes mean you can't stomp them, but they will react to just about anything else. They've lately picked up a few new tricks, like Buzzy's trick of walking on the ceiling and curling themselves back into ball form so they can float on water.
 * Spike Top: The worst of both worlds, a Spike Top can neither be stomped (because of its namesake spike) nor fried (because it has the same type of fireproof shell). Also, they are very skilled at crawling along walls and ceilings, tuning the corners quite easily so as to keep going. But there are ways to beat them (shells, Super Stars, knocking around the block they're walking along, etc.).
 * Para-Beetle: Unlike other winged creatures, Para-Beetles are virtually invincible. Indeed, you usually don't want to defeat these creatures because they tend to appear in wide-open areas; you'll need to hop on their backs and hitch a ride in order to get across the vast empty expanses they cross.
 * Heavy Para-Beetle: These larger versions will appear in only one course. They have difficulty enough as it is flying so the moment you land on it, Heavy Para-Beetles will start to sink from the sky. Be sure to find another place to land before it takes you with it.

Cheep-Cheeps

 * Cheep-Cheep: These fishy foes are dangerous, despite their appearance. They dwell underwater, and often appear in massive schools of 5-10. The fire flower works best - stay slightly above them and fire!
 * Mega Cheep-Cheep: A, uh, big Cheep-Cheep. Less prone to hanging out in schools, but if frozen, their large bodies mean that they can easily shatter on nearby obstacles - use this to your advantage!
 * Deep-Cheep: Green Cheep-Cheeps that are a little more cantankerous than their red cousins, Deep-Cheeps will swim towards Mario as long as they are in front of him. The method for defeating Cheep-Cheeps above works well on them, too.
 * Mega Deep-Cheep: A, uh, big Deep Cheep. That is all.
 * Eep-Cheep: The opposite of a Deep-Cheep, yellow Eep-Cheeps respond to Mario by swimming away from him. For protection, Eep-Cheeps also tend to swim in schools.
 * Spiny Cheep-Cheep: These fellows take the whole 'chase Mario' thing to a whole new level - they just won't give up the chase! Even for their small size, Spiny Cheep-Cheeps can be deadly, and often appear close together in groups of around 3 or 4. Worse, they fight back if frozen, tending to break free almost immediately.
 * Porcu-Puffer: These huge Spiny Cheep-Cheeps usually are only seen on the surface, where they pursue Mario and even try to leap out of the water to attack him.
 * Cheep-Chomp: This rare but dangerous fish is big enough to eat people whole, and he's developed an appetite for heroes. Stay away from his mouth!
 * Fishbone: A cross between a Cheep-Cheep and a Dry Bones, these skeletal fish tend to inhabit enemy lairs. Once they lock onto you, their eyes turn red and they speed towards you like a torpedo, even to the point of crashing and falling to pieces.

Other Water Enemies

 * Blooper: A squid that constantly moves to pursue Mario whenever in the water. Blooper swims in a strange but predictable pattern, always drifting in Mario's direction. If Mario is below, Blooper simply sinks slowly, but once Mario is above, Blooper will repeatedly lurch upward to try to catch up.
 * Blooper Nanny: These mother bloopers spawn Baby Bloopers and then release them in order to attack Mario.
 * Baby Blooper: Unlike Micro Goombas, these tiny Bloopers can hurt you. Avoid them!
 * Urchin: Urchins will float in the water along a predetermined pattern. You usually need to swim around them, but they can be defeated by fireballs and so on. If they're frozen, though, they'll quickly break free but then just sink. This can be handy as an Urchin is just the right size to block a water current pipe.
 * Big Urchin: Larger versions of the above, but so tough and ornery that only a Super Star can defeat them.
 * Huckit Crab: These new enemies only appear in one level, but they appear everywhere in that level, attacking you by building and throwing balls of sand. At least they and the sand balls can be stomped.
 * Clampy: These clams try to lure you with treasures like 1-Up Mushrooms. Watch out, though, because they can suddenly shut their shells on you and hurt you.
 * Bulber: These passive lantern fish only inhabit one level. Because they're passive, they're best left alone as their lantern lures help to light up the dark level.
 * Jellybeam: These appear in the same level as the Bulber. A little more active than the Bulber, they move up and down but also light up the way in the darkened level. Like the Bulber, they're best left alone, though if you have an Ice Flower, you can freeze them to make them less dangerous.

Artillery Enemies

 * Bullet Bill: These projectiles are constantly launched from Koopa cannons, both on- and off-screen. They constantly fly forward in the direction they're fired unless stomped or otherwise dealt with (though Bullet Bills are fireproof). Keep in mind, though, that these days Koopa cannons can be oriented in all sorts of directions, including at angles.
 * Banzai Bill: Pretty much what you'd expect from a super-sized Bullet Bill. They otherwise act the same.
 * Bull's-Eye Bill (aka Missile Bill): Watch out for these smart Bullet Bills. They have the ability to sense when they've overshot you, change course, and keep chasing you!
 * Bull's-Eye Banzai Bill: At least these huge projectiles are so big they can't track you so well. They'll try to track your height, but at least they can't turn around.
 * King Bill: The biggest of all Bills appears in only one level, but this juggernaut of a Bill is unstoppable, barrelling its way through anything that dares to get in its way!
 * Bob-omb: Living bombs that walk around trying to pursue Mario. They tend to come in a never-ending stream from pipes. Hitting them stops them so you can pick them up and throw them, but it also lights their fuses! Get them away before they explode!
 * Para-bomb: Bob-ombs coming out of the pipes is one thing, but these rain down on you from above! Stomping on the chutes grounds them, turning them into regular Bob-ombs.
 * Chain Chomp: These relentless "guard dogs" will periodically lash out at anyone that approaches, limited only by its namesake chain. If he's tied to a stake, you can release it from the stake, causing it to rush headlong until it hits a wall. A larger version is also used by Iggy to pull his chariot.
 * Fire Chomp: Fire Chomps float along the sky with several fireballs in tow. In addition to chasing you, it occasionally shoots one of these fireballs towards you. Best to stomp these while it has a fireball to spare, because if it finds out it's out of ammo, it goes on a kamikaze charge: counting down to an explosion!
 * Amp: These electric sentries patrol predetermined areas of enemy lairs. Though usually avoided, you can freeze them.
 * Rocky Wrench: The mechanics aboard Junior's airships. When they see an intruder aboard, they'll pop out from their covers and throw their wrenches at you.
 * Mecha-Koopa: Wind-up Koopas that mindlessly progress forward in pursuit of Mario. Stomping on them temporarily stuns them so you can pick them up and kick them as weapons.

Ghosts

 * Boo: The ever-haunting tenants of the Ghost Houses, Boos don't like being looked in the eye; they'll cover their faces and freeze, but the moment your back's turned, they'll resume the chase.
 * Big Boo
 * Circling Boo Buddies: This gang of ghosts circle around a predetermined area acting as a guard. You must look for the gap in their formation in order to make your way in and out of them.
 * Broozer: This mean-tempered ghost is itching to go a few rounds with you. They only appear in the World 7 Ghost House, where they charge at you once they see you, breaking any bricks and knocking over any barrels in their way.
 * Scaredy Rat: Quick-moving little annoyances in the Ghost Houses, they get skittish and jump around if you get close, and if you defeat one Scaredy Rat, any others nearby will beat a hasty retreat.
 * Ghost Vase
 * Crowber: Swift and dangerous birds that make dive-bomb attacks in the late stages.

Fire Enemies

 * Podoboo: Living balls of lava which jump out from fire pita in an attempt to scorch Mario. Time your jumps for when they're not around.
 * Firebar: Chains of fireballs that form a straight line and swing around in a circle from one end. Proceed past these flaming gates very carefully.
 * Fire Snake: Another living flame. This one hops from place to place, sometimes up and down platforms, chasing Mario. Careful, as they've learned a new trick. After a couple hops, their heads can flare up and grow huge for a few seconds.

Others

 * Monty Mole
 * Swooper
 * Pokey
 * Bramball
 * Spike
 * Stone Spike
 * Wiggler
 * Mega Wiggler
 * Cooligan
 * Fuzzy
 * Mega Fuzzy
 * Foo

Object/Obstacles

 * Cannon
 * Cannonball
 * Giant Cannonball
 * Rocket Engine
 * Spiked Ball
 * Giant Spiked Ball
 * Spiked Pillar
 * Giant Spiked Pillar
 * Ball 'n' Chain
 * Firebar

Fortress/Castle Enemies

 * Dry Bones: The re-animated remains of long-dead Koopas. They are fireproof, and if you stomp one, it only stays down for a few seconds before reassembling itself and starting up again. You can smash them for good, however, if you freeze them first.
 * Super Dry Bones: A larger Dry Bones that requires Ground Pounding to break apart. They will react to freezing, but they can break out much more quickly.
 * Thwomp: Huge stones that sense intruders and will drop themselves to the ground if you get too close. Try to lure them into dropping then getting out of the way. Then you can cross as they try to get themselves back up to dropping height again.
 * Super Thwomp: Pretty much as one can picture it: a much-larger piece of rock that otherwise acts the same way. Still, being so big, getting out of its way can be rather tricky, especially since it's so heavy that it can smash through bricks, meaning they can't be relied upon for protection. But since it's so big you may find crevices in the floor you can hide in to avoid its crushing bulk.

Bosses

 * Larry Koopa
 * Roy Koopa
 * Lemmy Koopa
 * Wendy O. Koopa
 * Iggy Koopa
 * Morton Koopa Jr.
 * Ludwig von Koopa
 * Kamek
 * Bowser Jr.
 * Bowser
 * Giant Bowser