I've begun to comile a list of all the characters at the end of the 100th episode. This proved more difficult than I thought it would be at first. First off, the episode I just downloaded on BitTorrent is not that great of quality and making the picture size bigger makes a lot of the characters hard to make out. Add to that that half of the characters I either don't recognize or just don't know their name. But anyways, here is my list so far, feel free to download the episode and/or add any names to the list and please post it.
A spot with a comma after it denotes a character in that position who I don't recognize. A spot with some sort of description in it denotes a character who I recognize but don't remember name or that have no official one.
List at end of 100th episode: 9 rows starting at top, from left to right
1-11 characters 2-13 characters 3-20 characters 4-17 characters 5-16 characters 6-18 characters 7-12 characters 8-8 characters 9-2 characters
total-117 characters
1st row: , Nurse Gollum, Big Gay Al, Chef, Jesus, Mr. Garrison, Mr. Slave, Priest , Terrence & Phillip, . 2nd row: Death, Doctor , SeaMan, Drew Carey, Gorak/Steve, , , , Cheech & Chong, Joseph Smith, David Blaine, . 3rd row: Towelie, (Genetisist), Man with No Face, , Jared, Hat McCullough, Sally Struthers, Krishna, , Mohammed, , Mr. & Mrs. (butt faces), , (time machine guy with glasses), two Marclars, , Wendy, Starvin' Marvin. 4th row: , , , , , , , , , , , , , , , (ranch owner), . 5th row: , Lolly, , , , , , , , , , , , , Jimmy, Professor Chaos/Butters. 6th row: (bus driver), Timmy, , , , , , , , , , , , , , (6th grader in LOR parody ep), Halfy, . 7th row: , , , , , , , (bar tender), , , , . 8th row: Mr. & Mrs. Stotch, Principal Victoria, , , Mr. & Mrs. McCormick, Mr. Mackey, , Mr. & Mrs. Brovlofski, Mrs Marsh, Mayor, , , Ned, Jimbo. 9th row: Mr. Marsh, .