Say what you will about the live-action movies, but the a capella versions the Chipmunks sing of Bad Day and Funky Town are pretty damn awesome.
When Dave steals the muffins after being rejected
For The Squeakquel:
In the second movie, Alvin and Simon going completely Papa Wolf on the bullies that're picking on Theodore.
Ian Hawke's Heel–Face Turn: He spends most of the movie helping Dave find the Chipmunks. In a way, does re-kindle his relationship with Dave as they rescue The Chipmunks. He even convinces Zoe to save Dave from falling off a fallen log with a big Heel–Face Turn speech.
Ian: It's tempting to blame Dave. I know. I've been there. I wish I could take back all those years I spent plotting my revenge. All that time and energy wasted. All those pizzas I had delivered to his house wasted.
Dave: Ian, that was you?
Ian: Not now, Dave! Alright? You can let Dave fall to his death, and I could go back to the raft with the Chipmunks, become their manager again, and make tons of money, so really I'm good either way. But let me tell you something: Hate, anger, regret. Those aren't just members of a girl-group I once signed. They're what consumed me. And they're consuming you. It's not to late to do the right thing...Or again. I'm good either way. So I don't wanna sway you.
Someone took the original covers and slowed them down so the vocals are at standard speed, resulting in sludge-y, intense instrumentation and slow, near-depressed pop-style vocals. It's better than it sounds. It's been christened "Sludgepop", and consensus is that it's awesome.