Grounded on the 23rd Floor - S1-E5
Continuity mistake: Zack and Cody skate in the lobby and push a guy with a golf bag. It falls and spills the golf clubs onto the floor. A big guy trips on it and falls over Mr. Moseby, and after that the golf bag is not seen. (00:00:35)
Grounded on the 23rd Floor - S1-E5
Continuity mistake: In the episode 1x05 "Grounded on the 23rd Floor", Zack and Cody give all the candy for a camera. They put it all on the table, but when they get the camera, all the candy is gone. (00:08:00)
Grounded on the 23rd Floor - S1-E5
Continuity mistake: In the episode 1:05 "Grounded on the 23rd Floor", when Cody falls from the porthole, two glasses are on the floor, but later when they run after the papparazi, the glasses are gone. (00:15:45 - 00:18:25)
Grounded on the 23rd Floor - S1-E5
Continuity mistake: When Carey opens the suite door to find Moseby with the hotel bill, then when the room service arrives and in the following shots, the twins' backpacks' straps are on, then off, then on, then off and so forth.
Grounded on the 23rd Floor - S1-E5
Continuity mistake: When Carey is confronting the boys, she places her hand on her left hip twice.
Answer: Keep in mind, Muriel wasn't very popular. So the writers/directors must have thought it'd be a good idea to let go of the character. No one seems to be complaining.