We found this idea on JHS Englipedia, and after some heavy modifications (mainly due to taste) we produced this worksheet (click to download).
The concept is simple. Students have a copy of the sheet each, and work in pairs to decide who would win in a fight of cuteness, coolness, etc between the given characters.
NB: You might want to change some of the characters if, by some miracle, time has elapsed since this sheet was made and the fickle Japanese public no longer recognises them.
You can also add a bit more interaction by not printing the characters on the back of the sheets, but rather making students work in larger groups (2-6) and come to you for their next assignment - assign an envelope to each group, and give them a card with two characters and a challenge "hungry", "cool" etc. out of it each time they come to you. Make it a race to finish all the cards. This is slightly more hassle to perform, but if you find your kids like that sort of thing then it may be worth it.
At the end you can ask volunteers to read out their answers.
Lasts about 20 mins the simple way, and 25 if they receive cards from you one at a time.