_ForgeUser1197795 1) First i'd like to request a terminology change... The word "critter" normally means a level 1 ambient small animals, like frogs, rats, sheep, etc. See related [To All The Squirrels I've Loved Before] achievement or http://www.wowwiki.com/Critter. The things which you can summon however are called companions (or small pets, or vanity pets), see http://www.wowwiki.com/Companion.2) Second important feature would be to recognize passenger mounts. Currently the only types of passenger mounts are mammoths and mechanochoppers, however there is a chance Blizz will add flying passenger mounts in future patches as well. I believe these mounts should go into separate category and have a separate keybinding to summon them.
