Mr. Mouse Takes a Trip (1940)

Continuity mistake: After Mickey hides Pluto in his suitcase in Burbank, Mickey picks up his cane and runs to the train, then when Mickey actually jumps onto the train caboose he's only carrying his suitcase, he does not have his cane, nor does he have Pluto's suitcase (which had been filled with bones) with him. The cane reappears on the train later, and at the end Pluto's suitcase mysteriously reappears when Pete throws it at the duo in Pomona.

Super Grover

Continuity mistake: When Mickey hides Pluto in his suitcase, the entire handle to the suitcase breaks off and Mickey tosses away the handle. This handle reappears unbroken when Mickey takes Pluto out of the suitcase and then quickly hides him again, though it's broken again in following shots. Then at the end, when Pete tosses both suitcases off the train Mickey's suitcase has the broken handle, but when it lands on Mickey and Pluto the handle reappears unscathed once again.

Super Grover

Continuity mistake: There's a hole in Conductor Pete's right shoe sole which repeatedly disappears and reappears.

Super Grover

Pete: You know, I used to have a little cat once. And when it was left all alone, it'd cry... meeeeeeeeeoooooooowwwwwww.