It's finally happening! The "Invasion!" crossover is here and "Supergirl" is meeting up with "Arrow," "The Flash" and "Legends of Tomorrow." It's definitely the biggest moment in The CW's DC universe and possibly in comic book TV as a whole.

What are you getting into when your favorite heroes fight aliens, though? Luckily, Screener knows exactly how it's going to go down. Here are 10 spoilery teases to get you adequately pumped for "Invasion!"

1. Metahumans are the root of the problem

The Dominators have come to earth primarily because of Metahumans. While their exact goals have yet to be revealed, it's those with superpowers -- and the threat they pose to the universe -- that have captured the alien group's attention.

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2. Get ready for a blast from 'Arrow's' past

We already know a few of the returning characters thanks to the photos of Laurel and the Queen family back from the dead in the 100th episode of "Arrow"... But they're not the only familiar faces you'll see sprinkled throughout the installment. Keep yours eyes open, because there's a lot of exciting nods to the show's past.

3. Barry's message to Rip Hunter plays a big role

Remember the message from future Barry that was uncovered on "Legends of Tomorrow"? Not only will Barry hear it during the crossover, it becomes becomes a pretty important plot point.

4. Diggle continues to have the best reactions to everything

You've seen Diggle's reaction to Supergirl -- but wait until he has to fight aliens. Per usual, Diggle is all of us in the way he reacts to the crazy world he now lives in.

5. The team is incomplete

While the 100th episode of "Arrow" does have a family reunion vibe, there's one current cast member that's missing from the celebration. See if you notice who's not there.

6. No, they didn't forget about Wally

Just because there's a crossover doesn't mean "The Flash" can ignore Wally's metahuman powers. "At the end of ['The Flash'] episode 307, Wally became a speedster. That’s huge. That’s big news," executive producer Andrew Kreisberg says. "To sort of gloss over that and not have anybody react, considering the myriad of reactions Joe has had to Barry becoming a speedster and Iris finding out. It felt like we’d be doing a disservice to the people who were watching 'The Flash' and enjoying it."

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7. The crossover makes way for fun character pairings

Supergirl and Heat Wave? Check. Oliver and Kara? Check. Cisco and Felicity? Check. Professor Stein and Caitlin? Check. The writers clearly had fun mixing and matching characters from different shows -- and it'll leave you dying for more crossovers.

8. Everyone knows who the most powerful superhero is

Oliver is great at archery, Barry is super fast, Sara is a skilled assassin and while that's all impressive, there's only one Supergirl. Luckily, the shows realize that and treat her as the asset she is. She can't do it alone, though.

"We’re certainly not the first writers or producers who have had to deal with the 'Superman conundrum,' which is, 'Why do you need everybody else when you’ve got a Superman?'" Kreisberg admits. "Hopefully, we created enough situations in this to show that just because you have Supergirl doesn’t mean you’re invincible. Everybody has a role to play as well."

9. The West family isn't on the sidelines this year

Last year's crossover was great, but shockingly light on Joe and Iris West. That's not the case this year, as the pair -- and Wally -- definitely play a role. Not only are they deeply involved in deeply involved in Wally's road to becoming Kid Flash, but Iris is there for the massive team up.

10. This isn't the end for the Dominators

Don't expect the crossover to mean death to all Dominators -- they're not going anywhere just yet. While they may get dispatched on Earth-1, "Supergirl's" world is an entirely different story. Kreisberg confirms the aliens will be heading to that show later in the season.

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The "Arrow"-verse crossover airs Tuesday (Nob. 29) through Thursday (Dec. 1) at 8 p.m. ET/PT on The CW.

Posted by:Chris E. Hayner

Chris E. Hayner is equal parts nerd, crazy person and coffee. He watches too much TV, knows more about pro wrestling than you do and remembers every single show from the TGIF lineup. You may have seen him as a pro-shark protester in "Sharknado 3." His eventual memoir will be called "You're Wrong, Here's Why..." TV words to live by: "I'm a firm believer that sometimes it's right to do the wrong thing."