My Raikou was my favourite. Unfortunately I totally messed him up because I wasn't aware of EVs and IVs etc so I just trained him through the Elite Four and at other trainers which gave most exp LOL.
My ditto was fun to see level up aswell. I had put him into the daycare center to breed the heck out of him. I caught him at like lvl 50, and he has been lvled up to about 82-ish just because of the daycare center.
That ditto must have loved his life. xD