Karofsky (Max Adler) is expected to be a big part of the upcoming 'Born This Way' episode, which will be extended to 90 minutes.
Speaking to TV Guide, McHale confirmed that Karofsky will be involved in the instalment.
"It has to do with Karofsky but not necessarily in the expected way," he said. "I think how they approached the whole way is unique. It's cool and the number is really nice and strong, the way we do it with the message."
McHale also revealed that he is enjoying working with Kristin Chenoweth again, who has returned to the show to reprise her role as April Rhodes.
"We filmed this number with her the other day, and I have to say she is a genius," he said. "I could have watched her all day. She is so funny. So she is back in a big way."
Glee returns for a new episode in the US on April 19 on Fox. The show continues in the UK on Mondays at 9pm on E4.