Continuity mistake: When Tiger and Fievel are doing their musical piece, Tiger wipes off the mirror and they appear the same size. When he lays out in front of the mirror, singing the line "We'll be there to pick each other off the floor", he places his head next to the cage bottom, still laying on the floor between them. In the mirror, however, that cage bottom is not reflected at all. (00:57:30)
Continuity mistake: When Fievel is first heading down the storm drain, as he believes his father is playing his violin, he leaves his hat on the surface, but a few seconds later he is seen holding the hat as he gets closer to the gang of cats.
Continuity mistake: Watch the small bed inside the water tower. Soon after the song 'Somewhere Out There', a small piece of cloth appears from nowhere on it. (00:41:10 - 00:43:15)
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.
Continuity mistake: Just before Gussie leaves Mickey O'Hare's wake, Fievel can be seen in the background behind Honest John eating a large piece of cheese from a nearby teacup. However in the next shot he's standing in a completely different location and no longer has any cheese in his hands. (00:40:05)
Continuity mistake: When Fievel is running after Tony in the back alley, he gets stuck in a sewer grate hole and hears what he thinks is Papa's violin coming from down below. Throughout the scene at some points, Fievel instantly appears in different grate holes. (00:48:20)
Continuity mistake: After the Giant Mouse of Minsk lands in the ocean, a vacant pier can be seen from an underwater perspective. But once the angle changes seconds later, all of the mice are suddenly looking down below at the wreckage. Additionally, two ropes appear from nowhere hanging over the pier's edge. (01:04:30)
Continuity mistake: At Mouse Garden headquarters outside of the Commission of Immigration, several vendors are trying to sell things to a crowd. Below a top hat is a sign which distinctly reads 'Mouse Garden'. But fast forward to the one offering a used ticket to Chicago right near the headquarter entrance and you'll see how it now says 'Immigration Mouse Garden' instead. (00:24:35)
Continuity mistake: When Fievel sits on the Statue of Liberty's torch, his right hand repositions itself between frames. First it's between his feet, then the outside of his left leg. (00:20:40)
Continuity mistake: During the storm, Fievel crawls to the edge of the step he's on and watches two fish flop around below deck. Keep an eye on his blue hat. At first it's in his left hand, but between shots the hat somehow jumps below the step he's on - from which he pulls it out with his right hand and places it back on his head. (00:16:10)
Continuity mistake: During the opening dialogue of "Never Say Never", Henri stands on the edge of a hot water bottle dressing Fievel. In the following shot Henri is standing on a container adjacent to the bottle instead. (00:22:00)
Continuity mistake: When Warren T. Rat grabs Fievel from behind the glass, his hand has a grip around Fievel's blue pants at first. But as soon as the shot changes, Warren T.'s hand is gripping bare ankle instead. (00:51:25)
Continuity mistake: When Fievel discovers that Warren T. Rat is actually a cat in disguise, the hat tucked into his black belt disappears between shots. (00:51:20)
Continuity mistake: When Fievel is looking out the tailor shop window thinking of a way to escape, his hat disappears from his belt between cuts. (00:28:55)
Continuity mistake: In Warren T. Rat's first appearance, he counts coins and places them into his overstuffed coat pocket. But when the shot changes to a closeup of Digit appearing from within the pocket, Warren T.'s hand is suddenly elsewhere, offscreen. (00:25:00)
Continuity mistake: When Warren T. Rat gets exposed by the mice and sets fire to Professor Digitalus' Museum, the word 'professor' is missing from the marquee at some points. (01:01:00 - 01:02:30)
Continuity mistake: After being bullied and tossed into a puddle, Fievel convinces himself that he'll never be able to find his family. Between shots, his arms cross themselves in a different manner. (01:09:35)
Continuity mistake: When Fievel is being pursued by a gang of cats, he runs into the museum and tries waking everybody up. At one point his left leg slips itself into his pants between shots. (00:59:35)
Continuity mistake: After Gussie knocks a growling cat in the head from atop the museum marquee, several mice suddenly appear to her right in between shots - tossing various objects at the other cats below. (00:59:55)
Continuity mistake: When the mice are scaling a rope towards the ship bound for America, Fievel - holding onto Papa's tail - stumbles a second time and points out a smokestack coming from the funnel. But at some point between shots, Fievel loses his grip on Papa's tail. (00:08:35)
Answer: Warren T. grabbed Tiger and told him he was fired.Tiger did eventually leave some time after that though.