The Flash, Arrow , Supergirl and DC's Legends of Tomorrow casts coming together and getting to interact was arguably the best part of The CW's latest DC crossover event, "Invasion!" Our Legends of Tomorrow review calls Invasion a "very epic and satisfying finish" to the arc. But unsurprisingly, some of the fun character moments had to hit the cutting room floor.

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At a recent "Invasion!" screening event, executive producers Andrew Kreisberg and Marc Guggenheim talked about the moments from the crossover that almost made it in, but ultimately needed to be cut. "It’s amazing how many of them we actually got to keep," said Kreisberg. "This episode came in wildly over, not surprising. And you’ve got to keep the plot going, and you had to have room, especially in these episodes, which probably had even grander visual effects sequences than we’re used to in an average episode, so it tended to be those little jokey moments that fell by the wayside. ... It was making sure that we were preserving as many of those little exchanges as we could."At the event, Kreisberg and Guggenheim also shed light on the episode's reference to Routh's role as Superman in 2006's Superman Returns With the Arrowverse's "Invasion!" crossover now concluded, let's take a look back at the scenes that didn't make it into the four-show event.Spoilers for The Flash Arrow and Legends of Tomorrow "Invasion!" episodes continue below.

1. The Dominators' Comics Mythology

The Dominators in DC Comics

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2. Lynda Carter as Earth-1 President

3. Aliens' Impact on Earth-1

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4. Supergirl on the Waverider

5. Sara and Alex

6. HR's Team Value

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7. Roy and Tommy's Roles

The Dominators almost looked a lot more similar to their comic book counterparts, but one pesky element of the adaptation got in the way of their green robes: CGI."Originally we had designed the Dominators with the green robes that were very iconic of the comic. When we decided to do all the Dominators full CG as we ended up doing, the robes had to go away because the presence of the robes made animating them prohibitively impossible," said Guggenheim. "But we've got these cool designs of like, 'Oh wow, they really look like the Dominators of the comics.'"Kreisberg explained that the crossover also originally explained the Dominators' culture more. "There were a lot more nods to the comic book. There was discussion about the size of their circles and how that was indicative of where they stood in the caste system," he said. "I'm sorry some of that stuff went away just because it was great flavor, and I think people who are fans of the original comic book would have seen a lot more of our joy at adapting Invasion in there, but it just unfortunately, to get these down to the proper time, that's the kind of stuff that tends to fall by the wayside."With Lynda Carter playing the president on Supergirl's Earth (Earth-38, for the record), there was some talk about her being the new female present on Earth-1 as well for an added parallel between the universes."In the original draft of the 'Legends' episode, she was the Vice President who became the President," said Guggenheim. "The studio had what we all considered to be a very fair note, which is it was a bit too confusing. You get into the parallel Earths of it all, but she's not the President on our Earth, she's the Vice President and, in the midst of time travel and aliens it just was -- as Oliver would put it -- one sci-fi problem too much. We thought OK, if the studio is getting thrown by it and confused, the audience might be too, so we took her out. Believe me, it was not for lack of wanting to. I was planning on being on set that day."The crossovers never established whether or not the world knew about the impending alien threat, and according to Kreisberg and Guggenheim, it's not going to be something that is further explored. There will be a mention on The Flash's midseason finale that "the threat of aliens brought out all the crazies," but Kreisberg said they're planning on "Doctor Who-ing it.""We had a line that we cut for time and just re-watching it, I was like, 'Oh I really wished we'd found the time another way,'" said Guggenheim. "There was a line where the character Glasses -- we call him Glasses because we're so original -- is he basically says, 'Cover up what? A dozen, you know, weather satellites falling out, you know, falling out of orbit?' Because people see the ships, but no one ever really saw the Dominators. The way we're sort of playing it going forward is that Glasses is good at his job, and when he says he's going to cover it up, he's going to cover it up."Supergirl was one character who never made it on the Waverider, but that might change in the future. "There was a Supergirl moment on the Waverider that I really wanted to get in there," said Guggenheim. "I’m not going to tell you what it is, because we may do it next year, but as you know Supergirl never ended up on the Waverider so we couldn’t do the moment."For all the people wondering what would happen if Sara Lance met Alex Danvers: you're not alone. "There was a little exchange between Sara and Kara that I really liked -- I don’t think we even filmed it -- where Sara says, 'Hey do you want to get a drink when this is all over,' and Kara says, 'I think you wanna meet my sister,'" Kreisberg said, adding he liked "just the idea of starting the Sara/Alex shippers going."Team Flash isn't the only group of Arrowverse characters noticing that HR isn't pulling his weight as much as some of the previous Harrison Wells were. "There was a funny scene between Speedy and HR where she says, 'So what are you doing here? What value do you bring?' He’s like, 'Well I’m writing a book,' and she’s like, 'Oh that’ll be a big help' and walks away," said Guggenheim of the cut scene.Though Colton Haynes and Colin Donnell ultimately weren't able to be a part of Arrow's 100th episode, they were originally written into the script on the off chance they were available."There were moments with Colton and Colin in Arrow that were scripted that we obviously just couldn’t do because of Colin and Colton’s availabilities," Guggenheim said. "For example, Roy was going to be Thea’s boyfriend -- that hadn’t changed -- and they met when he stole her purse, and that also hadn’t changed. I just thought that would have been fun and nice to see."

Terri Schwartz is Entertainment Editor at IGN. Talk to her on Twitter at @Terri_Schwartz