The scene with the Cartoon Bomb. "Some days you just can't get rid of a bomb!"
This recently became utterly hilarious in hindsight given that The Dark Knight Rises would later recycle this particular scene as its climax.
At the very end after the Security Council is re-hydrated. The way West delivers those lines are just plain HILARIOUS.
It gets better. Right before they leave, Robin and Batman glance back, watch the Security Counsel bicker in their new languages, and then turn away in a manner that suggests "Yes, we are definitely done with this. Let's leave, but inconspicuously." And then they leave. Out the window.
BAT.SHARK REPELLENT. Even better, the shark explodes immediately afterward (not that it makes any more sense, but the shark had a bomb in it).
The Penguin trying to trick his way into the Batcave as Commodore Schmidlap. How well does his disguise work?