Pokémon FireRed and LeafGreen/Saffron City

'Saffron City is home to the Silph Company, the makers of the fabulous Silph Scope. So how did Giovanni get his paws on the Silph Scope prototype? Is the company in cahoots with Team Rocket? The only way to find out will be to use a little industrial espionage, so get your team built up strong and prepare to go on a stealth mission!'

Team Rocket occupation
Fans of the TV show are probably beginning to notice that the ruthless Team Rocket of the game doesn't have a whole heck of a lot in common with the bumbling idiots depicted on TV. Their mission of world dominance has led them to Saffron City, headquarters of the Silph Company. Team Rocket has basically occupied the entire city, sending respectable citizens running while they force the staff of Silph Co. to make advanced weaponry for their nefarious purposes.

Mr. Psychic
Saffron's a pretty dull place for a city of its size. Outside of the Poké Center and the Poké Mart, there are only two buildings you can enter at this time. One is the Fighting Dojo (the left of the two Gyms at the top of town), and the other is Mr. Psychic's House (bottom right corner of town). Enter and he will give you your heart's desire — as long as your heart's desire is TM 29, Psychic. And it might as well be, since Psychic does a lot of damage, almost always hits, and has a 30% chance of temporarily lowering its target's "Special" statistic.

Mimic Girl
Once you've driven the Rockets away by reclaiming the Silph Company building, you can enter the house in the upper left corner of town. The little girl who lives here loves to mimic other people. She repeats everything you say, and you won't be able to have a normal conversation with her at all unless you bring her a Poké Doll. If you don't have one, head back to the Celadon Department Store to buy one. Give it to Copycat to receive TM 31, Mimic, in return. This skill automatically repeats the last attack done to you by your opponent. Not always useful, but at least virtually any Pokémon can learn it. Maybe now she'll feel less shy and be able to relate to people normally!

The Fighting Dojo
You won't get a badge for taking down this optional Gym, but you will get something just as good: One of two Pokémon that can be found nowhere else in the game. If you've only played the originals, you'll be in for a less-than-pleasant surprise. Beating the Mankeys in this gym is still easy, but thanks to a Generation II fighting move Foresight, the Machops, Machokes, Hitmonlee and Hitmonchan can still decimate your entire party even if you have Ghost Pokémon, so make sure you level your party up plenty before taking on this gym. When you've bested the Karate Master, he'll offer you your pick of his pets.

Flying types rule against fighting ones, so if you've been working on a Pidgey, you're in luck. Psychic types are also super effective here. Dark, normal, steel, rock, and ice types will be tested, as fighting is strong against them all.

Gym Battle
You can't get into Sabrina's Gym until you've saved the Silph Co. President within the Silph Company building. Only then will the Rocket blocking the door go away, and you can enter Sabrina's maze of teleport squares.

The least confrontational way to reach Sabrina is to take teleporter A, then walk straight up to B, then straight across to F, triggering one trainer fight, then straight down twice to I and M. You can avoid the trainer fight all together if you hug the bottom wall as you go from B to F.

Bug Pokémon are strong here, so a Parasect or Butterfree should be okay against Alakazam. The best way is to take advantage of her Psychics' weak defense with strong Ground, Flying, or even Normal Pokémon. Dugtrio and his Dig and Earthquake works well, as well as Raticate's Super Fang, which cuts the Pokémon's HP in half.

Defeating Sabrina will net you the Marsh Badge as well as TM 04, which contains the move Calm Mind. The Marsh Badge gives you the ability to command Pokémon as high as level 70, although you're not likely to have need of such power for quite some time.

Sabrina also has two hyper potions that will restore her Pokemon's HP completely, so be prepared for that. Mr. Mime also knows the Baton Pass move, which will randomly switch it out with one of Sabrina's Pokemon.

Items
Nugget: (hidden) found next to the computer in the northwest corner of the Mimic Girl's room