The Wrath of the Lich King brings us even more great new features for our pets. In the old game, we had to individually level a pet along with us. If we wanted a low level pet, we had to run him around and manually level him up all the way to catch up to us. Now pets will auto-level up to 5 levels below our level. For example, if you tame a lv 20 pet and you're lv 70, your pet will jump to 65 when you summon him. If you stable a pet and just leave it there, it will also auto level to catch up.
Hunters also now have 4 available slots in the stable for their pets. They can purchase these for a very reasonable amount of gold, and have a total of 5 pets (4 stabled and 1 active). This should make a lot of hunters very happy when they want to get a new pet without losing their old ones.