Project Rub, on the DS.
You could poke her with your stylus in the uhm... yeah. Baby hole?
She freaks out, naturally, or well at least I think she does. Her gestures let me suspect she didn't appreciate it, but since her 'face' is just a black silhouette, I could never truly confirm my suspicions.
...aaaaand before you all think I'm some kind of sick perv, I got the game with my DS when I bought it second-hand. And since the game is pretty terrible, I started messing around with all the features and looking for hidden extra's. Well, I sort of found a hidden extra, I think.