After being stranded on an island Alvin says to Brittney (and Theo hears) that he doesn't think that Dave is coming because Alvin drives him crazy" but Dave finds them they make up and the rest of the movie happens
Dave takes the Chipmunks and Chipettes on a cruise ship so they can get to the International Music Awards. Alvin gets a parachute and flies away with the rest of the Chipmunks. The end of the parachute is tied to Dave's lounge chair, and it drags his chair across the boat. He wakes up and tries to parachute up there to get them, but Ian works on the ship and holds him back. they both end up falling in the water and get stranded on the same island the Chimpnuks did.