Uncommonly used, but still heard once in a while. It's a phrase that Winnie from Animal Crossing would use every now and then (and I imagine that a few other characters similar to Winnie would use it too). Fun to say if your bored/hyper.
You're really giving me this cookie?? Yay! Super-happy-fun-time!
A laugh with slight guilt or embarrassment. More often typed than said aloud. Also, it is said by Rikku when she is in the Thunder Plains in the game Final Fantasy X. She is scared of lightning, and starts laughing like this.
Person: What? You really accidentally went into the wrong bathroom??
Person 2: Eheheheh... Um... Yeah. But not on purpose!!