Hee. If everyone realized you can't be too old to play with things then I wouldn't have problems going out in public with my tama on a lanyard like I do. She starts beeping and everyone looks offended when I pull it out and do something.
I'm 24. Everybody I know couldn't believe that I'd go out and buy something like a tama for myself. Of course these are the same people that go out and get themselves miniatures for D&D and consider that more dignified. Or they go and play with their kids toys, or play that newest x-box game or something. I'm like, uhnhunh.
But I tell some about their virtual pets, and about how much fun they had before they killed it. (Specifically my one friend. She gave me a pet because she couldn't take care of it, it kept dying on her.) I think I might win over more adults.
So yeah. I laugh when people under the age of 20 ask if they're too old. You're never too old for anything. Especially when it's about having fun. (You don't know how hypnotizing baby toys are until you're playing with those darn things. ROFL...
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So, in passing here, consider yourself kinda a tamagotchi embassador. You are one of the few, the proud, the brave enough to think that toys are fun even past childhood. You can't convince everybody that there's nothing wrong with it, but hey, you can change some minds.