Well, I think the character your tama evolve into sometimes can depend of the care, but it's not true that you will have e.g. Masktchi only if you take bad care of your tama.
It's very easy, you just have to press B button (the one in the middle) when your tama is near to the hurdle. You have to figure out when is the right moment. The more hurdles you've already jumped over the faster your tama goes. There are 30 hurdles.
Well, I don't do this, but I won't say it's a bad thing. I don't want to do this, because for me it's more fun when you don't know whch character your tama will become :mellow:
Well, I'm sure I saw here, on TT, screen with the pssword for this picture (I now that it wodn't work for other tamas, but it woud mean that somebode already have it! ) when I looked for info about souvenir 32 few days ago. I'll try to find this again.
EDIT:
I'VE GOT IT!
Look at this...