Ds10 doesn't typically get this 'into' a game, but lately he has been bonkers about 'Flip Notes'. It is a mini animation studio, he downloaded it (he's got the DSi, which can get on the internet), and he does nearly nothing else now!
I mean I rarely have had to tell him to put his ds down in the past, but now it is becoming more of a 'thing'. I don't mind too much as I think he is learning the basics of animation and I have seen some really amazing things he's done (amazing for a 10 year old). He is pushing beyond his usual story-telling and he doesn't seem to mind that it takes a really long time to make these, his focus is startling.