Kim Possible: A Very Possible Christmas (2003)
This Christmas episode was almost entirely comedy, focused around Ron Stoppable (Kim's partner) and Drakken (her bumbling nemesis). Normally, that might grate on me, but here it seemed to work. The writing was snappy and clever, with the exception of a running gag about X-Treme sports that didn't age well.
The episode did a good job juggling the absurdity of Kim's world, along with the trappings of holiday cheer, and while the result wasn't Earth-shattering, it was absolutely entertaining.
If you're flipping through the channels and stumble across this, I definitely recommend giving it a chance.