I actually do a Happy Dance, mostly stomping my feet up, with my arms close to my body, elbows bent, and waving my fists from side to side. If it sounds geeky, it’s because it is geeky. Added to that is that fact that I can’t dance.
The moves vary, but it’s always nekkid. So, y’know, be forewarned when using it.
I’ll just add to the list of Snoopy/Peanuts dancers.
I just substitute lap for happy.
It ain’t always good - some posters don’t form pretty mental images.
Ed Grimly
Woody from Toy Story does a particularly happy dance…that’s what I’d picture.
Not Snoopy, but the Peanuts kids dance in “It’s Christmas, Charlie Brown” with lots of bouncing and arms akimbo and then drawn in, and toes pointed in pigeontoe style, then out in ballet first position style, and head bouncing left to right and back again, over and over. That’s my happy dance.
And I just did it, just this moment, just for kicks. Whoo! Happy dance!
Another ‘Snoopy’ dance here…
Though Schroeder’s holiday dance is a close second. The ‘cabbage patch’ dance comes in third - It really depends to a large degree on my mental image of the poster which one I picture.
I always thought it had at least some elements of one of those NFL touchdown dances (Terrell Owens’ fer instance)
Like clog dancing, but with much smiling & waving of the arms. 
That’s what I picture too. Glad someone else with more Buffy info posted. 
Snoopy.
And I thought I would be the odd person out when I thought it looks like the Snoopy dance.
Well, either the Snoopy dance, or the cabbage patch. One of the two.
I, too, picture the Snoopy dance. That’s the only way it can be. 
Another “Snoopy” vote checking in.
Bingo, that’s it precisely. Alternately, as TeaElle said, the Peanuts gang dancing like in the Christmas special.
The happy dance I always envision is Lorne’s brother Numfar’s Dance of Joy that he performed in the Angel S2 ep “Through the Looking Glass”: kicking and hopping side to side while bonking oneself randomly on the head.
For some reason I think of some dude in cowboy boots jumping in the air with his hands on his sides while clicking his heels together. And smiling. I guess it is sort of like Snoopy, but I want to be different. Maybe some weird square dancing Snoopy.
I think I’m #29 in the Snoopy queue.