Herb

Actual Name: Herb
Species: Rat
Nicknames:
Herbbie, Hibbles, H, Maggot (when he misbehaves), Maggoty Man, Herbamare

Lenny

Actual Name: Lenny
Species: Rat
Nicknames:
Len, Little Big Man, Leinster, Blinky (because he's blind), Lenstah, Leonard, Leonard's Corner, Leonard Nimoy, Brian Lenihan

Peter

Actual Name: Peter
Species: Rat
Nicknames:
Petey, Big P, P-Star, Big Man, Sir Snacks-A-Lot, Pedro (pronounced Paaay-dro, like Tayto from Into The West), Mister, Ball o'Wool, Petey the Brave

Harvey

Actual Name: Harvey
Species: Rat
Nicknames:
Harvs, Harvard, Harvey Weinstein, Lumpy (he had a lump), Monk (he had a bald spot when said lump was removed), Hivvard, Harvoid, Harvey Norman, Skinnymalink (he was skinny), Marvin, Harvey Pekar.