Topps is producing a trading card game based on the online game Moshi Monsters for release in the U.S. in 2011.  The game has already been launched in the UK, where the online game originated. 

Moshi Monsters Mash Up includes 145 different cards featuring over 100 different characters.  Some cards include fragments of a Moshi map with codes for virtual items on the reverse. 

Moshi Monsters is a free-to-play game with revenues derived from the sale of virtual items.  Over 20 million monsters have been created to date, with over two million new players joining each month. 

Topps also produces the Club Penguin TCG, based on a free-to-play online game owned by Disney.