I always liked the little touches in IK+, trousers falling down, worm walks across the screen, spider dropping down... lots of little things in such an awesome game just made it more 'loved'. When I see little touches like that, it makes me think that the developer put a bit more effort in. Often though it's by accident, like in Oblivion you can have goblins chase you all over the game world by nabbing one of their staff things, there's lots of weird stuff in that game if your bored enough.
I always try and add something pointless to a game. Something that people might not even notice, it's not all about debugging

- sometimes even the bugs are the most entertaining part, especially with enemy characters. I mean, the first time an AI character kills the player, well you just want to give it a hug! - it's usually been through hell to get there. Making AI years ago for a FPS game was damn hilarious, having tough terrorist looking guys determined to shoot you in the left toe is pretty funny.
I think game development would be pretty boring if you weren't allowed to have a little fun, add a bit of personality here and there - it'd be pretty dull to be too good at it as well, you'd miss all the shenanigans.