The current fastest growing Facebook games: another popular virtual pet game in PetVille, while Crazy Planets appears to get the kind of attention that its originality deserves, and a quick look at two competing poker games, veteran Texas HoldEm Poker and new kid on the block Poker Rivals.

Zynga let its latest game off the leash over the weekend, a virtual pet game called PetVille, neatly slotting into a couple of Zynga traditions - it follows the same naming style as FarmVille and FishVille, it does very well in encouraging users to check back on a daily basis, and it's aiming at an established niche that Zynga hasn't yet dominated. Playfish's Pet Society has been sitting comfortably in the overall Top 10 leaderboard for some time now, and CrowdStar released Happy Pets (8 million monthly users) halfway through November. Naturally, Zynga's dominance of the Facebook games scene gives them extra leverage when promoting new games to their existing users, so fast growth for PetVille can be expected. Despite a recent data collection glitch that artificially inflated PetVille's growth to 97% (it's closer to 33%), it's still making very impressive headway.

Like PetVille and number eight ZooWorld, data on Crazy Planets has suffered from the same glitch and a more accurate daily growth reading would be between 10% and 15%. Still, it's been receiving the kind of interest that most Facebook games crave. The game has been out for nearly five months, making it a venerable old thing by Facebook standards, but still displays that rarest of things: originality. It's a cutesy interplanetary conflict with interesting gameplay, and each player's alien defense force are in fact space-suited and booted miniatures of people on their Facebook friends list. Of course, like many successful social-network games there are perks for recruiting and playing with friends, and it's a little surprising that Crazy Planets hasn't garnered more playtime since the summer. With this recent growth spurt there is hope that Crazy Planets is getting the attention it deserves.

Texas HoldEm Poker, again from Zynga, is standing strong at number 10, but just outside our chart lies Poker Rivals, the first competing poker game with a strong chance of success, and again from Playfish. It's the first post-aquisition title from them, now that they are under the wing of videogame giant Electronic Arts. Released on November 27, Poker Rivals boasts 100,000 daily users from a two and a half week total of approximately 425,000. Smallfry perhaps, when compared to Texas HoldEm's millions, but with an overall 20-25% of total users coming back on a daily basis it's certainly doing something right - Texas HoldEm is securely locked in to the same percentage spread.

The Facebook games with the biggest increases in daily active users on December 8 at 15:00 GMT are:

1. PetVille (934,945 = +913,851 / 97.7%)
2. FarmVille (28,407,350 = +817,180 / 2.9%)
3. Pet Society (4,948,441 = +396,493 / 8.0%)
4. Happy Pets (2,591,872 = +228,864 / 8.8%)
5. Restaurant City (4,680,805 = +137,943 / 3.0%)
6. Crazy Planets (385,163 = +104,123 / 27.0%)
7. Roller Coaster Kingdom (2,273,475 = +96,929 / 4.5%)
8. Zoo World (714,341 = +83,114 / 11.6%)
9. Fish Isle (766,530 = +65,491 / 8.6%)
10. Texas HoldEm Poker (4,603,192 = +58,309 / 1.3%)

Numbers in brackets relate to total daily users, the increase in daily users, and the daily percentage growth.