Continuity mistake: When we see Hans walking down the rope from the boat, he's carrying plain pink cloth. But when we see Hans the next time, the cloth now has white spots on it.
Continuity mistake: When Hans is speaking to Willie in the lift, Willie's tail keeps disappearing and re-appearing.
Continuity mistake: The lighter that burns Sylvester's whiskers wasn't there when he opened the drawer of the filing cabinet.
Trivia: When Hans arrives in America, he gives his cousin Willie some cheese. Hans then looks around and sees some traffic coming past. The traffic includes a pink lorry saying "Foster's Eggs" and a yellow lorry saying "Fritz Transfer Co." - a reference to the writer Warren Foster and director Friz Freleng, respectively.
