Luckily, "Glee"'s producers have realized Rebel Wilson would have been perfect on their show - hopefully, she'll finally agree to guest star! (Universal Pictures)

Shockingly, this “Pitch Perfect” star auditioned for “Glee” when it first began and was not chosen to be part of the cast. Since, then the show’s producers have reached out to Rebel to guest star and we can only hope she can fit it into her schedule. Her outrageous personality would be a perfect fit for the show!

Drake Bell

Okay, so Drake Bell has previously told El Universal that he does not want the show to cover any of his songs. Sigh. But, if he were to ever come around, he should really consider guest-starring. He could break out the guitar and get back into “Drake & Josh” mode.

Ashley Tisdale

Remember her “High School Musical” years as the ever so fabulous Sharpay? This girl can sing and has expressed that she would be delighted to guest-star on the show, if given the opportunity. She would make a great diva to challenge the New Directions.

Amy Poehler

She’s hilarious. She’s great on TV. We’ve even heard a sample of her singing at the Golden Globe Awards (seen below). Imagine her as Sue Sylvester’s sassy co-coach or a seductive new teacher at McKinley High. Even viewers who are not Gleeks would be tuned in!

Madonna

It was a pretty big deal when “Glee” aired their Madonna-inspired episode. Why not bring back the greatness and have the legendary singer herself grace the “Glee” set? She could teach the McKinley kids a thing or two about how cool singing is.

How has this gorgeous face not been on "Glee" yet? (Twitter)

Justin Timberlake

Really, how has it taken this long for JT to make an appearance on a show like “Glee”? Coming on the show would be perfect for his comeback into music, but actually, we just want him to grace our TV screens again.

Hilary Duff

This Disney idol has been in retirement for some years now with her own little family unit. If she ever chose to get back in business, she could guest-star on “Glee” as a mentor or a singing coach. We all know she’s still got vocal talent in her.

Adam Lambert

There have been plenty of rumors circulating about the “American Idol” runner-up. But he has not been on “Glee” yet and we are still patiently awaiting an appearance from the rocker. He can serve as an inspiration to the New Directions and teach them a valuable lesson about standing out from the crowd.

Reach Associate Entertainment Editor Kathy Zerbib here; Follow her on Twitter here.