Game: eat your heart out!

There are students and there are students.  Some you can tease and play with mercilessly and they'll think you're the greatest thing since sliced bread; others will go home broken hearted if you look at them wrong.  Nearly all of them forget to conjuguate verbs correctly.

I had a student who would regularly turn in amazingly creative works of fiction all without conjuguating a single verb!  Drove me nuts!  This after all was level 7 of 8.  But we got along well, so one day when he turned in a paper, I took 10 seconds to glance at it and told him "I see 8 mistakes in here.  If you can correct them in 3 minutes or less, you can have this lollipop."  I set my timer and walked away.
3 minutes later my timer went off. 
"Teacher, I can't find any mistakes!".
"Sure you can!" I said as I unwrapped the lollipop and cheerfully began to eat it myself.
The next day, I found half the number of mistakes and in 3 minutes he'd corrected them all and won his lollipop.

There are three elements in this story that show that it's about a game:
1. The obvious one: the lollipop.  The prize helps.  However, adding prizes willy-nilly does not a game make.  School itself is all about points, awards and prizes, but no-one would call it a game.
2. The arbitrary rule.  Why 3 minutes?  Why not?  Most games are fun and challenging precisely because they have arbitrary rules.  Golf, for example, is pretty silly: if you really want to put a ball in a hole in the ground, there are surely easier ways of going about it than by hitting it with a stick from a distance.
3. The sense of "evil" fun.  The student pretended to be furious when I ate the lollipop and was determined not to be bested the next time.  And the next time, he wasn't!