Heads up Supergirl fans -- especially those who've had a hard time dealing with Kara (Melissa Benoist) and Lena's (Katie McGrath) recent turmoil -- you're going to get a serious kick out of the show's 100th episode! It feels like just yesterday that we all watched Supergirl debut on CBS (its Season 1 home before moving to The CW for Season 2), and yet somehow it's almost time to celebrate a huge milestone episode for the show. Now, we've got some solid details about the episode's plot, including an explanation for how we'll be seeing a lot of familiar faces return.

The episode synopsis reveals that Mxyzptlk (Thomas Lennon) returns to grant Kara a wish (his specialty) to go back and time and see how things would have turned out if she'd told Lena the truth about her identity before Lex could. Using this It's a Wonderful Life-inspired narrative tool, the episode will look back over key moments throughout the series, leaving Kara with a pretty huge decision: does she want to change history to save her relationship with Lena?

"The most exciting part -- because we know we have a lot of people coming back -- is just getting to work with cast members that I've not gotten a chance to interact with on set before," Nicole Maines told TV Guide on the red carpet for Supergirl's 100th episode party. "Also, just getting to see everybody together was just really fun!"

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We've been wondering which beloved characters from the past will return and how for the milestone episode. And while the who is still up in the air, at least we know why we'll be seeing these fan favorites again. The one character we've been eager to get answers about is Mon-El (Chris Wood), Kara's ex and fellow alien refugee who left the series after Season 3. Knowing that we'll be revisiting the past makes it much more likely that we'll see Mon-El once more, given he was part of quite a few key moments from the show. Not to mention, the rivalry he started with Mxyzptlk to win Kara's heart was so hilarious we'll almost be disappointed if we don't get to see those two go at it again.

"I was in Vancouver during the hundredth episode," Wood told TV Guide, when asked whether we should keep our eyes peeled for Mon-El. "And I went to the party. And that's as much as I can say." Just like Mon-El, it looks like Wood will remain evasive with his future knowledge.

We're going to remain cautiously optimistic that Mon-El will make an appearance, and in the meantime, we'll keep our fingers crossed for appearances from other fan-favorites like Maggie (Floriana Lima), Cat Grant (Calista Flockhart), and maybe even some other Arrowverse stars!

Supergirl's 100th episode airs Sunday, Feb. 23 at 9/8c on The CW.

Chris Wood, Supergirl

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