Continuity mistake: When the doorman sees Sylvester and Tweety going into their rooms, you can see that Room 1001 (Tweety's room) has a door handle on it, but when the doorman leaves Sylvester's room after accidentally walking in, the door handle on Room 1001 has gone.
Continuity mistake: When the doorman goes to the lobby to order all pets out of the building, you can see he has a star on his waistcoat. The star disappears when he finishes his announcement, and in the next shot it is back again.
Continuity mistake: When Sylvester's owner tells him that she will get into the hotel, you can see that she is wearing a brooch on her shirt. But when she is carrying Sylvester around her neck in the next shot, the brooch has vanished.
Continuity mistake: When the doorman comes up in the lift and sees Sylvester chasing Tweety, the walls by the lifts are coloured blue, but when the doorman leaves Sylvester's room later on, the walls are now green.
Continuity mistake: When Sylvester leaves his room to deliver the note under Tweety's room door, you can see there is nothing on the wall between the two doors, but when Tweety goes over to Sylvester's room, a green square has appeared.