Continuity mistake: When Warren takes Fievel to his henchman Moe who is a rat, he is the same size as Moe. He is even able to go through the very small hole in the wall into the room. Later in the movie, Warren is now seen being the same size as a cat.
Other mistake: Fievel and his family are Russian and live in Russia at the beginning of the movie, but only Fievel's parents have Russian accents, whereas Fievel and his sister have American accents. This is especially odd since they end up immigrating to America.
Answer: Warren T. grabbed Tiger and told him he was fired.Tiger did eventually leave some time after that though.