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!
Used when one is describing smoking marijuana. Can be applied as a substitute for the word marijuana/weed when asking another in a public setting to detract others from what you mean. Think stealth.
Person 1 (at work): Hey are you down for a super happy fun time session?
Person 2: Hell yeah I'm down.