"I'm Dr. Diminutive and I don't have a Napoleon complex, Napoleon had a me complex! Don't cross me!" — Dr. Diminutive with an important insight into his character[src]
Dr. Diminutive is an evil scientist and a member of L.O.V.E.M.U.F.F.I.N., also known as The League Of Villainous Evildoers Maniacally United For Frightening Investments in Naughtiness. This mad scientist has lost all hair except around the temples and wears glasses. He is named for his short stature, and due to that, makes him the shortest member in L.O.V.E.M.U.F.F.I.N.
He was first seen in "Nerdy Dancin'" at the press meeting for the formal introduction of L.O.V.E.M.U.F.F.I.N., where he pointed out to Dr. Doofenshmirtz that there was no press. The group then went to the taping of Let's All Dance Until We're Sick, which was where the press was. He was soon kicked out for bad dancing and crushed by falling debris from Agent P. In Agent Doof, thanks to Dr. Doofenshmirtz, Dr. Diminutive sees that his rival Newton the Gnu is agent silent G and uses it as an advantage to successfully capture and defeat Newton. When the OWCA learns this they send Perry the Platypus and Doofenshmirtz to stop Dr. Diminutive. Diminutive learns that his colleague has now joined the OWCA as a good guy, and uses a hologram to lure them into the path of a particle bubble he fires to trap them. He then puts his new rivals in Newton's cage and tries to drop them from 40 stories high. When he lets them drop, Perry uses his technology to steal the Particle-Bubble-"Erator" and then shoots Diminutive into a bubble. Perry then saves Newton, Doof and he by using a new particle bubble to shield their fall and bounce back to OWCA headquarters.
Dr. Diminutive was later seen in "Bullseye!" as he was disqualified from the L.O.V.E.M.U.F.F.I.N Pageant of Evil because of his height, implying that "I don't have a Napoleon complex, Napoleon had a me complex!"
His name is very fitting because the word diminutive means extremely or unusually small which as we can see he’s very short
He appears to make -erators instead of -inators or -inizers ("Agent Doof")
His nemesis appears to be Agent Silent G/Newton the Gnu. ("Agent Doof")
In "Norm Unleashed", he stood trial for allegedly stealing the Schmaltzinator and using it. The verdict was never announced, although he was next seen in a jail cell with Dr. Doofenshmirtz.