Glee has been with us for almost five years now — since May 19, 2009 — and the show is just a few months away from hitting a huge TV milestone. On March 18, 2014, the Fox comedy will air its 100th episode.

Season 5, Episode 12 is titled “100 and it will feature the long-awaited return of some very beloved favorites, including both Dianna Agron (Quinn) and Heather Morris (Brittany). Filming for the episode has only just begun, but we’ve already learned a thing or two about what to expect.

Take a look at the spoilers available so far and we’ll continue to update you as filming continues and more information leaks:

Credit: Twitter

Glee’s 100th Episode: Vote Now to Have Your Favorite Songs Performed on the Show

No new songs will be performed during the episode. Instead, each tune will be a remix of a previous favorite, all voted on by fans at the end of last year.

Ryan Murphy: Glee’s Original Cast Invited for 100th Episode — Dianna Agron, Too!

In early December, Glee creator Ryan Murphy took to Twitter to announce that “ALL The Glee Originals” had been invited back for Episode 100.

Dianna Agron’s Quinn Back for Glee’s 100th Episode — Confirmed!

Fans were very confused when Dianna wasn’t in Glee’s Cory Monteith tribute. The actress said she wasn’t asked to take part, while Ryan maintained that she never expressed interest to him in the first place. This time around all the miscommunication seems to be worked out. Ryan officially asked Dianna to be in “100,” and she said “yes.” Quinn is back!

Heather Morris’s Brittany Returning for Glee’s 100th Episode — Cast Reacts!

Also returning is Heather, who appears to have left acting behind to focus on her baby son, Elijah. But 100 episodes is a big deal, so HeMo has agreed to don that Cheerios uniform once more.

Glee Spoiler: Which Grads Are Returning for the 100th Episode? (UPDATE)

Heather and Di aren’t the only returning grads. See who else will be popping up in Episode 12.

Glee Season 5 Spoilers: Kristin Chenoweth Returning for 100th Episode

Apparently, “all the Glee originals” wasn’t limited to just the kids! Kristin Chenoweth is returning to reprise her role as Schue’s former love interest, April.

Glee Spoilers: This Original Actress ISN'T Coming Back for Episode 100

That said, this Season 1 staple won’t be returning.

Glee 100th Episode Spoiler: First Look at Rachel's Song (PHOTOS)

Prepare to break out the tissues.

Glee 100th Episode Spoilers: Originals Film Heartbreaking Scene

And not just one time, either.

Brittana

Glee Season 5 Spoilers: Brittana to Reunite in 100th Episode!

Brittany and Santana might be broken up, but that doesn’t mean they’ll avoid each other when Brit makes her big return. Nope, fans can for sure expect some Brittana scenes. (Commence fangirl squealing now.)

Glee's 100th Episode: Brittany, Santana, and Quinn to Sing Britney Spears?

This song spoiler is still only a rumor at this point. But it comes from a reliable source, and the idea of the Unholy Trinity doing a Britney song...well, that be just too good to pass up!

First Look: Heather Morris Is Back on the Glee Set! (PHOTO)

It's so good to see her back!

Glee 100th Episode Spoiler: Expect a Huge Brittana Shocker!

So, should we be worried... or really ridiculously excited?

Glee 100 Episode Spoiler: Lord Tubbington and Fondue for Two Coming Back?

Best. News. Ever.

Glee 100th Episode Spoilers: "Epic Kisses"... But Is Brittana Included?

Hmm. Looks like we're still going to have to wait to know for sure.

Glee's 100th Episode Spoilers: Santana and Puck Pole Dancing (VIDEO)

Hot.

Quinn

Remembering Finn

Glee Spoiler: How Finn Will Be Remembered in Episode 100

He might be gone, but he is certainly not forgotten.

Glee 100th Episode Spoiler: Finn's Death to Be Addressed in "Significant Way"

Giving the gravity of this milestone episode, we're glad the show is once again taking time to honor Finn.

Music

Glee Music Spoilers: 100th Episode! Rumored Song List for Season 5, Ep. 12

Wicked's "Defying Gravity" by Rachel, Kurt, and Mercedes

Britney Spears's "Toxic" by Santana, Brittany, and Quinn

The Zutons's "Valerie" by Brittana

Avril Lavigne's "Keep Holding On" by Puck

Pharrell's "Happy," performed by April, Blaine, Holly, Mercedes and Will

Pink's "Raise Your Glass" by Will and April