I was just thinking about the possibilities for Nintendogs 2 and I came up with Yoshiogs and Pokéogs. Cats wouldn't do so well because real cats aren't that trainable, but little Yoshi's or Pokémon theoretically are, so would make an interesting spinoff.
Normally I would write this kind of idea down in my little black book, but no way will I ever need this idea for myself, so I post it.
I like the Pokémon idea the most because it would bring the gamer closer to what is shown in the cartoon series and this would be a great progression for the Pokémon franchise. I can just imagine training sessions with Pikachu striking targets with lightening. Or even an adventure mode where you take him out and go on adventures around an MMO environment with other players, battling and doing quests.
"Come here Pikachu"
"Stop that"
"Over here Pikachu"
"lightning attack"
Arrr what fun.