When you turn the game on you see the little worker villagers scurrying away from the cactus or rock back to where they're supposed to be, research table, farm, etc? It's not that they're done celebrating or anything. I think they're just getting caught goofing off pushing that rock or whatever they do up there when I'm not looking.
I think it's funny how they do the "OOPS! Boss is looking, act busy!!!" thing hehehe.

Yes I notice it all the time! I actually have villagers who sit there with the maternality ladies and they say "unsure what to do" (altho I assigned them a job). But as soon as I stare at the some more, they suddenly get to work! LOL