UPDATE: Considering how many hits this post is getting per day, I'll make it plain and clear - You will not find the answers to Wowhead's Easter contest here, sorry. Wouldn't want to ruin the spirit and fun of their contest, not to mention undermine all the hardwork put into creating it! Good luck hunting elsewhere for tips and clues. :)
Wowhead is giving away TCG prizes as part of their Easter Egg hunt contest, and amongst the TCG loot is a TCG pet! 10 third place winners will receive a Gregarious Grell, while other winners will receive packs or even whole collections which may contain loot cards.
To enter, you'll need to have a Wowhead account. Solve the riddles listed on the contest page and visit the database page for each answer to each riddle. You'll be entered into the contest by receiving a holiday Wowhead achievement after you've visited the correct answer page.
For more information, check out their contest page linked above. Good luck to all those entering!