Facebook games have been known to feature limited edition collectibles to celebrate everything from Valentine’s Day to the Superbowl, but this might be the first time we’ve seen limited edition items as cross-promotion. Starting today, one Zynga game will spill into another as FarmVille collectibles will be made available to PetVille players for a limited time.

The FarmVille collection will feature 10 different items with a different item becoming available each day for the next 10 days. The first item, a FarmVille farmer, will be available until tonight at 11:59pm Pacific time. Each item will only be available for one day so you’ll need to log in regularly if you want to complete the collection.

The items are available exclusively through the in-game gifting system, meaning you can send FarmVille collectibles to friends but can’t actually purchase them for yourself. If you don’t have any friends playing PetVille yet, this is a great week to get them started. Click here to send your first gift now.