If I remember properly, they go into sleep mode when left alone, and you can send them to bed any time you want. But they will wake by themselves and cry. But I think there's a sound setting...?? The minipet units by themselves are cool because they have a big world to explore and lots of options for an American virtual pet, but taking care of them takes a long time. You need to take care of them a LOT to keep them at peak level, but they don't die, so there's no real risk. Also, caring for them takes a long time because for each action that you perform, there is an animation that lasts a while that you can't exit out of. So, good and bad. But, if you have the explorer plug-in game, the minipets are TOTALLY worth it. The explorer game is lots and lots of fun!