Not Bowser
Now wait a minute. Bowser is NOT the villian of the game!? Take a look at these real villians..
Count Bleck
The main villain of the game, he has many minions under him. He is an interdimensional villain who has acquired the Dark Prognosticus and plans to use it to destroy all worlds and make his own from scratch. His real name is actually Count Blumiere and his true love is Tippi, also known as Lady Timpani. Their real names are revealed at the end of the game.
Nastasia
Count Bleck's assistant. She has hypnotic and brainwashing powers. She often stumbles over her sentences, adding unnecessary words such as "Um" or "Yeah".
O'Chunks
A strong, Scottish, but very unintelligent minion of Count Bleck. He is sometimes late for meetings.
Mimi
A sadistic shapeshifting cute girl who transforms into a giant spider (known to her and the player as True Mimi) in boss fights. She is a minion of Count Bleck. She constantly changes dresses through every scene she appears, but is known for wearing a yellow dress with white polka-dots.
Dimentio
An evil magician, also a minion of Count Bleck, who controls his own dimension (Dimension D) and can create many copies of himself. He often adds similes to his sentence, and almost always smiles. He dresses like a jester. He turned into Super Dimentio once but Mario, Peach and Bowser defeated him.
Mr. L
Is he Luigi? He builds giant robots in order to fight the heroes. He probably became a minion of Count Bleck through Nastasia's brainwashing. He acts cocky and gives the Heroes of Light nicknames (Mario is Mr. Jumpsallthetime, for example. This indicates that Mr. L may have some memory of being Luigi).
Brobot
Mr. L's giant robot. Another piece of evidence that he is Luigi. Seriously, all you need to do is take Peach and use her umbrella by using it and gliding over Brobot. In another, you use Mario and the funny alien who has to go to the bathroom and you have to shoot Brobot. Just keep away from the rocks, and you'll be OK.