Sean Avery: Cheating on Mary-Kate Olsen with Lake Bell?

While Ashley Olsen and Lance Armstrong seem to be going strong, twin sister Mary-Kate Olsen had better watch her back with her new athletic star squeeze.

According to the New York Post, New York Rangers hockey standout Sean Avery, who met Mary-Kate Olsen through a mutual pal, Bungalow 8 owner Amy Sacco, is two-timing Mary-Kate and seeing his ex-flame, Lake Bell, behind her back!

Sean Avery (right) sure is pumped up after scoring... with Lake Bell!

What will Mary-Kate Olsen think when she hears this news? Who knows. But there are plenty of other NHL players chasing celebrity tail if she's interested.

Sean Avery is not exactly known for his gentlemanly ways, of course. New York Post sources say after he split with Elisha Cuthbert, Sean Avery went around telling people he dumped The Girl Next Door star, not the other way around.