The DVD has an optional language track...in Martian.
The Martian Emperor speaking in a high-pitched voice after inhaling the absorbed nuclear blast.
It's a blink and you'll miss it moment, but when Byron challenges the Martian Ambassador to a fight, the latter removes his cloak and reveals what looks like a championship belt. Just imagining the oddly proportioned Martians boxing frequently is just.. Really odd.
One of the darkest jokes in the movie, the little dog running off with Michael J. Fox's hand, all that's left of him after being vaporized, like it was a bone.
In the very last scene, within the destroyed ruins of the house, one woman is nonchalantly dusting.