ProfessorStone first used cows as a way to teach object-oriented programming in C++. It often involved the Cow class, which included member function addHat(). He would then draw a cow as a big circle for the body, small circle for the head, and a big U for its horns.
More animals were added during lectures for flipped learning by ProfessorTalvitie? and possibly ProfessorMedero?.
ProfessorMelissa? created the CS70 website, which was used for flipped learning exclusively until Spring 2024. It was used for one flipped section in Spring 2024, but ProfessorStone also taught two unflipped sections that same semester.
ProfessorMelissa? added the rabbit to indicate rabbit-topics.
ProfessorWloka? taught CS70 with ProfessorMelissa? and although he did not to the characters in the teaching portion, he would often make Progress Checks (mini-quizzes) involve a character Detective Whiskerton.
Detective Whiskerton is the alter-ego of his cat, Margo. ProfessorWloka? often would tell his son stories about Detective Whiskerton because his son tended to get bored on the way to school. ProfessorWloka?'s other cat, Klein, does not appear in the Progress Checks, but his alter-ego is Inspector Whiskertail because ProfessorWloka?'s mother kept misremembering the name Detective Whiskerton for Margo (so they just gave Klein this name). Because Detective Whiskerton and Inspector Whiskertail sound too similar, Prof. Melissa's cat was given the alter-ego Inspector Claws to join Detective Whiskerton in the Progress Checks.
Note: Margo is a black and very floofy cat with a very floofy tail, and Klein is a brown cat with a non-floofy tail and both are very cute :)