Steve Mighty: Averted; he's a normal guy with a normal name.
Matt O'Morph: A metamorph (i.e. a shape-shifter).
Dot Dash: Her power is super-speed (Dash), her first name is Dorothea (Dot), and "dot-dash" is Morse Code (married name Morse) for the letter "A" (maiden name Axel, which is itself a pun on "accelerate").
Dolly Bird: Has feathers, wings and beak of a bird, blonde hair and bustline like Dolly Parton. Also, she speaks with a British accent; "dolly bird" is British slang for an attractive young woman.
G-Nat: He's part insect (gnat), acts like a gangsta ("G"), and his real name is Nat (or Nate).
G-Nat's girlfriend, Julia Skimmer, has dragonfly-like wings. There is a species of dragonfly called the "julia skimmer".
S.B.D.: Simon Burke Davidson; his initials also stand for "silent but deadly", referring to the type of fart that makes no noise but is lethal in its odor. (Simon generates a similar odor when he turns invisible).
Violet Klein: She's seven-foot-one (or 2.18 metres); "klein" is actually German for "small". She does get smaller when she goes berserk; her superhero name is "Shrinking Violent" (a pun on "shrinking violet", meaning a shy person).
Carrie Pelosi: Her most prominent characteristic is her massive head of hair ("pelosi" is Italian for "hairy"). Hairy Carrie also has glasses with thick black frames, cheers for the Chicago Cubs, and says "Holy cow" ... all references to former sportscaster Harry Caray.
Ginny Free: Lee's mom. Her maiden name was Virginia Shenandoah West; a reference to the Shenandoah Valley in West Virginia.
Uma Quipleure: There is a brand of cheese in France called "La Vache Qui Rit" ("the laughing cow"). Since Uma and her father resemble cows, that would make her "la vache qui pleure" or "the weeping cow" (implying that she has a tragic past).
Also, the similarity between "Uma" and "moo" should be obvious.
Melvin Odious: The son of Professor Odious. He loves music; he's "melodious".
Cameron Odious: Mel's older brother, big and muscular. "Cam Odious" is pun on "commodious" meaning large.
Mecha-Nichole: A reformed villain who has a "mechanical" head. Previously she was Dr. Nichole Endyme ("nickel and dime").