I don't think Michael and Sophie were even two years old when I bought their first floor puzzle at a mom to mom sale. It became a favorite activity that came to include a ceremonial puzzle completion dance that must be performed on top of each finished puzzle. We have since acquired enough floor puzzles to fill a large bin plus half of a shelf in the playroom. A couple of days ago I challenged the kids to put together all of the puzzles all by themselves and pretended to think there was no way they could do it.
That's the same way I get them to clean up sometimes. I pretend that there's no way they'll be able to clean up the playroom all by themselves and am going to be super mad when they bring me back to see. Michael and Sophie give me smirk that shows they're into the game, and once they've finished cleaning, they find me in another room, tell me to close my eyes, lead me by my hand, and I pretend to be amazed by their achievement. I only use the trick occasionally as it works pretty well, and I don't want the effectiveness to wear off!
Sophie and Michael still haven't put together all of the puzzles at once, but they have assembled and disassembled them all over the last few days of deep freeze hibernation, leading me by the hand to see them one by one. I have helped a bit here and there, of course. None of us can resist a good puzzle.