Glee: How come Puck and Ken are in glee club?

I'm sorry.. I haven't been able to follow the show... I just saw an episode in where the glee club performs... in front of an audience... where there's Emma and Terri (Will's wife) and she sees Emma looking suspiciously glad at Will... but it's only Will, Finn, Puck, Ken and I don't know who else.. (only guys)... so how come Ken Tanaka (the football coach) and Puck (the football player) perform since they two both thought glee club was gay and ridiculous and stuuf..?