I love Patapatatchis. ^^ My second fave tama after Furawatchi.
You can get the big two (Mametchi/Mimitchi) from almost any teenager, right? So yeah, you have a chance with Patapatatchi. Getting a Young Mametchi/Mimitchi has no influence whatsoever on getting the adult counterpart - in fact, most people who get Young Mametchi/Mimitchi DON'T get the adult counterparts. Not always the case, though. I got a Mametchi from a Young Mametchi.