Continuity mistake: Once the chipmunks are inside the food cupboards, they begin to devour everything inside. Theodore is seen chewing off a corner of a box of Lucky Charms cereal and eating the cereal that pours from the hole. But a few shots later when the same box of cereal can be seen, the hole that Theodore gnawed from the corner of the box is gone and the corner is fully intact. (00:11:00)
Continuity mistake: When the chipmunks start practicing for the first time with Ian, Ian gives Simon "cooler" glasses that he should use it from now on. However, in their tour shots he's still using his old glasses. Much later in the movie he is also seen rummaging through a desk cabinet for his his old glasses which he found to be already bent. (01:01:50)
Continuity mistake: Towards the beginning when Dave leaves the record label (after he steals the muffins), downstairs you can see a girl in a pink top, a delivery guy and a black guy in beige boots. The girl in the pink top passes Dave, then it cuts and you see her in front of Dave. Then it cuts again and you see her behind Dave and going around a corner. Also, the guy in the boots does the same thing a few times. And the delivery guy comes up close to the shot in the end, then they show him again just getting close.
Continuity mistake: When the chipmunks are giving Dave the presents they got him, Theodore had made him a card out of a folded sheet of paper. On the front of the card he has written (and misspelt) "To Dav" - note this handwriting. From when the card is laying on the table to when Dave picks it the writing has changed. When it was on the table the T was crossed and the V was longer than the A. But when Dave picks it up the T is uncrossed and neat and the V is now the same size as the A. (00:45:50)
Continuity mistake: In the end, when Dave is chasing Ian, we see many headlights behind him. However, once the chipmunks hop up and Dave slams his brakes, we see no lights and no cars pass him. Also, the whole time they are talking, no cars pass again. When Alvin steers the car there are all kinds of cars again flowing both directions.
Continuity mistake: The pumps of chocolate sauce in the chipmunks' coffee disappear too quickly for them to drink it all.
Continuity mistake: When we see Dave making the shoebox house for the chipmunks and writing a letter to them, Dave pokes five messy airholes in the top of the box. However when he decides against the idea and puts the box up on a high shelf, now you can see that in the lid of the box there are now seven airholes and also the holes looks much neater than before. (00:37:00 - 00:37:55)
Continuity mistake: When Dave leaves his house for work, there is a skateboard leaning up against the wall by the door and there is an umbrella stand with a lot of umbrellas in it. But when Dave gets back home from work the skateboard is now on the other side of the door in the corner and there are now fewer umbrellas in the stand. (00:03:35 - 00:09:30)
Continuity mistake: On top of the white cabinets / cupboards that run along the kitchen is a whole row of glass jars, vases, pots, etc. During the whole kitchen scene, the actual jars and pots that are on top of these cabinets move around and rearrange in different shots. In the close-up of Alvin pushing over the packet of Cheese Balls for instance; you can see that the jars and pots on the cupboard above are differently arranged than in other wide shots of the whole kitchen. (00:11:15)
Continuity mistake: In the scene inside the house that Uncle Ian gave the chipmunks, Alvin has foam darts on three air-pump launchers. He fires all three of the foam darts from the launchers; and we see him standing on the table with the three launchers and the three attached air-pumps, nothing else. But in the next shot suddenly all three of the launchers have a foam dart readily attached to them! And in addition a large pile of foam darts has appeared on the table, behind Alvin. (01:00:30)
Continuity mistake: After Dave has caught Alvin from off his head and trapped him inside a woollen hat, the removal of the hat causes Dave's hair to get messy and parts of hair have fallen down over his forehead. But in the following shot his hair is neat and brushed back to how it was before. (00:13:15)
Continuity mistake: When Dave hears the chipmunks singing outside on the tree trunk, he goes and opens the window to hear them better. The window to the viewer's right (from outside) has its slatted blinds down - and they are also closed. But after the chipmunks finish singing 'Funky Town', the same blinds aforementioned are now open. (00:16:10)
Continuity mistake: Inside the house that Uncle Ian gave the chipmunks, the chipmunks are all playing with the new toys they have received. Simon and Theodore are on a trampoline and Alvin is playing around with foam darts. In one shot we see four foam darts shoot across the room in succession - however there are only three dart launchers. (01:00:30)
Continuity mistake: When Dave gets back from Jett Records he enters his music study, removes his jacket and throws it into a blue plastic box. He then takes his keyboard and throws it outside. Then when he comes back into the study we can see the box again, but now his jacket is no longer inside it. (00:09:50)
Continuity mistake: When Uncle Ian arrives at Dave's house on Christmas, he comes in with a huge pile of gifts as well as a huge Santa sack full of presents for the chipmunks. When he walks through the door with the sack the door swings to a shut behind him. But in the next shot more people from Jett Records walk through the same door with more gifts - only now the door is wide open for them. (00:47:25)
Continuity mistake: When Dave comes back home with the food that he has bought he discovers that the chipmunks have completely cleaned his entire house for his date. When he comes inside and stops to look at how clean the living room is, watch the slatted blind on the door behind him. In the first shot the slats are closed, but when Dave walks into the kitchen the slats are open. (00:31:55)
Continuity mistake: Alvin pushes over a packet of Cheese Balls and they fall from the cupboard and into a bowl that is on the kitchen counter. He then cannon-balls from the cupboard into the bowl of Cheese Balls which causes a lot of them to fall out of the bowl, spilling all over the counter. However when Dave walks into the kitchen and spots the bowl, the amount of cheese balls on the counter (around the bowl) is much less. (00:11:15)