I agree, make the pets from the Leaderboard events available randomly in the Tree House...those of us who were around for those events ended up with the pet habitats but no pets, so this would give us another chance at obtaining them. Also, any pets from previous events (excepting specific events like birthday events or the election; those should probably be purchasable instead) could be offered through the Tree House.

I also wouldn't mind a few more animals for the special pet habitats (that don't already have at least 3 available, not counting duplicates), like a couple more goats, another turtle, another ghost/spirit, something else for the igloo, etc. These could be won through events...maybe an Xmas seal, or a New Year's goat.