Continuity mistake: Right at the start, when Zack is hanging on the tree branch, the long sneaker laces are in front of Cody's shoulder, but when Zack falls, they're gone, though the sneakers have not moved.
Continuity mistake: When London and Mr. Moseby crash through the wall with a car, there's a white betong-block on top of the car, but a few shots later, it's turned itself around a little bit more to the middle. (00:12:35)
Continuity mistake: Zack and Cody's mom takes away the rats to Zack and Cody's bedroom. She goes behind the sofa, but in the next shot of the door, she's not to be seen anymore.
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)
Continuity mistake: In the episode "Commerical Break," they start to film the commerical for the first time without London and with Mr. Mosby. London gets upset and sits down on a couch where they are shooting the commerical. She and the couch leave the shot for a second, and London is gone when they show the couch again.
Continuity mistake: In "Boston Holiday", Zack is talking to Mr. Moseby in the hallway. In a wide shot, behind Zack, you can see that the elevator door is closed. But when it cuts to a close-up, the door is suddenly open. There wasn't enough time between shots for the door to open.
Continuity mistake: Zack puts Cody's whistle in their mate's pudding, but when Cody says, "You got pudding on my whistle" and the mate says, "And you got whistle on my pudding," the whistle is gone from the pudding, between shots. Then, a few shots later, we see that Cody is holding the pudding drenched whistle. (00:08:00)
Continuity mistake: In the scene where they are having the finals, the things on the desk change a few times.
Continuity mistake: When Zack and Cody finally come to the stage, Cody has a sock over his sweater and it's still there when they start singing. But in an instant the sock is gone. Cody could not have taken it off, because he was too busy playing piano.
Christmas at the Tipton - S1-E21
Continuity mistake: Season 1, episode 21 'Christmas at the Tipton': When Arwin leaves to fire up "Old Betsy", he trips over the couch and when he breaks the table its broken pieces differ between shots.
Continuity mistake: Season 1, episode 22, 'Kisses and Basketball': The twins' mom is sitting in the back and she has her hands down. When Arwin says "Let's kick some" it cuts to their mom and she has her hand on her neck, it then cuts back to the basketball team and she has her hands down by her lap again.
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.
First Day of High School - S3-E10
Continuity mistake: In Season 3, "First Day of High School," when the principle is telling London that she cannot build her lounge, the position of her hands change from being on her hips to being in the air.
Continuity mistake: Season 1, episode 16 'Big Hair & Baseball': In the lobby, when Cody comes to the defense of Moseby, Zack is holding two ice cream cones and as he continues eating, more of the ice cream appears between shots.
Continuity mistake: Season 1, episode 19 'Ghost of 613': When London finds her gold purse in suite 613, she places it on her left arm just as the noise at the door scares her, but when Cody tries to jump into her arms the purse is on her right arm.
Grounded on the 23rd Floor - S1-E5
Continuity mistake: When Carey is confronting the boys, she places her hand on her left hip twice.
The Suite Life Goes Hollywood (1) - S2-E36
Continuity mistake: After eavesdropping on Bud and Lou, when the 'hitmen' open the door, the things on the tray Bud is holding keep moving around between shots.
Neither a Borrower Nor a Speller Bee - S2-E12
Continuity mistake: When Maddie is painting the apartment, London is reading the article about Porsche's charity work, and the actual newspaper changes between shots.
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.