Charmander is the fierce and aggressive one, willing to kill for his own gains. He is extremely witty, over-confident, and sarcastic. 

Bulbasaur is the pleasant one, and is very agreeable. However, he is sort of a psycho because he wears Pokémon body parts (Particularly a severed Caterpie (Pablo’s) head, as a hat), and tries to eat himself. 

Squirtle is the only somewhat normal one, being reasonable. He prefers using empathy to solve problems, and encourages Charmander to do the same.