Petz is already a hit on the DS.

OCT. 2, 2010 • Ubisoft has an online free-to-play MMO version of the Petz virtual pet simulator planned for release sometime in 2011. Petz World gives fans of the franchise the chance to explore with their pets, adopt pets, and save endangered Petz. The franchise has sold more than 20 million units over various platforms.

Impact: In the new DFC report, The Market for English-language Client-Based PC F2P Games, we state that much growth in the market will be driven by established publishers bringing known franchises out in some sort of F2P version   Petz is a perfect example of this and is clearly the type of franchise that has some proven success online.  For example, Neopets, prior to being acquired by Viacom in 2005, built a very substantial audience.