Huge fan of science, rambling about it so often, showing off his inventions and smugly explaining how they work; it's his passion, something that's obvious.

And what's also obvious is the fact he is not the most mentally sane out of his family; Raph, the tough softie, Leo, the goofy but reliable leader, Mikey, the cheerful but wise little brother that acts as the family therapist. Donnie isn't crazy, just a little deranged.

And also commits tax fraud as well as a few other crimes each and every year. He steals from ATM's, but the government hasn't caught on yet since he covers his tracks. He is a genius, after all.

So when you knock on his door, Donatello opens it with a lazy, "What?" Sipping his coffee and staring down at you.