Tracy Jordan=hilarious
Tracy and Kenneth together= triple times hilarious
Kenneth-because of his child-like exuberance, especially his "way of seeing the world" (on last Friday's episode)
Jack Donaghy-Alec Baldwin is amazing in this role. Very fun character, and the one that's most complex. To me Alec and his portrayal of the character, with that "talking like this" voice, seems like someone in a Batman movie (one that comes into my mind is "Batman Forever"---in a role as ally or antagonist, unsure). Don't know why, but I just do.
Liz Lemon-Love Tina Fey, who for some reason I think of as a dog (I can see different people as animals)---and not just "dog", but "top dog"; and not just any dog, but...Scooby Doo (!) Why? From what I've gathered, they (at least Liz anyway) both like food, they're easily frightened, they have funny catchphrases (Blurg, Ruh-Roh, Mewt, Rike, etc.) and they have mini-mes.