Of all the things we know about Glee's Cory Monteith/Finn Hudson tribute episode (Season 5, Episode 3: "The Quarterback"), Dianna Agron's (Quinn Fabray) absence raises the most eyebrows.

Dianna, who left the show to pursue a movie career, is one of only two major former cast members who did not return for the tribute to their dearly departed castmate. The other MIA actress is Heather Morris (Brittany), but since she's a little busy being a new mom, that omission makes sense. Dianna, on the other hand, does not have a baby on the way. Given how connected Quinn and Finn's stories have been, fans were shocked to find out that she won't be featured in the episode at all.

What happened? Was Dianna too busy with her budding movie career? Was she not asked back? Is it because of her rumored feud with the cast and crew of the show?  Reports and statements about the situation are conflicting, and it's impossible to know what really went down behind the scenes. What we can offer is a rundown of what everyone has said. It's up to you to draw your own conclusions.

Dianna Agron: Dianna herself told the New York Post that she wasn't asked back for the episode, and thinks she might not get to return at all this season. In the interview she expressed surprise that Quinn, formerly a central character, could be dismissed with such ease.

Ryan Murphy: Of course, if you ask Ryan Murphy, the problem may be that Dianna never reached out to him. While he hasn't explicitly addressed Dianna's absence, he stated that he added actors into the episode if they called him to express a desire to take part, implying that Dianna was left out because she never asked to be a part of the tribute.

Is it because of past drama? Sources told Radar Online that the problem is a feud. According to the sources, Lea Michele (Rachel) and Ryan Murphy "intensely dislike Dianna and have both worked to marginalize her as much as possible. They never saw her as a team player,” and “simply did not want her sharing the glory for this very special episode.”

Could that report possibly be true? Multiple sources told E! Online that the rumors of strife between Dianna and other members of the Glee team are totally false. Let's hope so!

A scheduling conflict? E!'s sources claim the problem was much more mundane: Dianna wasn't actually available when the episode was filming. That's why she didn't ask to come back, which connects to Ryan Murphy's statement above. Dianna's movie career is certainly moving forward, so we wouldn't be surprised if it all boiled down to Dianna being a busy bee.

Are you upset Quinn won't be in the episode? Which explanation do you believe? Sound off in the comments below!

Watch the Cory Monteith tribute episode tonight, October 10 at 9 p.m. ET/PT on FOX.


Rebecca Martin is an Associate Editor at Wetpaint Entertainment and our resident Game of Thrones, Breaking Bad, and genre TV expert. Follow her on Twitter and Google+!