While Spore isn't out yet – the creature creator is available and it allows you to make many different types of monsters. The lead guy for Spore, Will Wright has hinted towards how he might turn Spore into an MMO. To note is that Wright is the person behind Sims Online which did not go as well as he hoped.
Wright explains how Spore is well-known for being the first Massively Multi-Player Single Person Game, which might sound a bit confusing. However, Wright goes into details to explain what it really means.
"There was nothing between the two," he said, adding that Spore will cater to this space "where you have a lot of players connected through content, but it's not synchronous: it's asynchronous interactions."
"The biggest benefit I saw from that was the possibility of having a collaboratively built world, that's huge and always surprising," he explained. "So for Spore we tried to figure out, how do we get the best aspects of a massively-multiplayer game without all these huge design limitations?"
"I think a lot of these limitations were what sank The Sims Online: we didn't have enough user-created content; to a lot of the people that were playing The Sims, the idea of paying a subscription was a really big filter - a lot didn't even have credit cards."
Read more here.