'Avengers: Endgame' used never-before-seen footage from 'Thor: The Dark World' for a key time-travel sequence, including Natalie Portman's appearance

• Warning: Spoilers below if you have not seen "Avengers: Endgame."
• In "Endgame," Rocket (voiced by Bradley Cooper) and Thor (Chris Hemsworth) time travel back to Asgard during the events of the 2013 movie "Thor: The Dark World" to retrieve an Infinity Stone.
• In the process they sneak past Loki (Tom Hiddleston), and Jane Foster (Natalie Portman) makes a cameo.
• Coeditor Jeffrey Ford told Business Insider that in both instances unused footage from "The Dark World" was used.
• "The shot of Loki throwing his cup in the cell and Thor and Rocket sneak past him in the background, that's a piece of digital negative taken from the dailies of 'The Dark World' that we repurposed," Ford said. "The same for the scene of Natalie Portman."
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It turns out Natalie Portman didn't have to set foot on the "Avengers: Endgame" set to be a part of one of the biggest box-office hits of all time.

Portman reprised her role as astrophysicist Dr. Jane Foster from the first two "Thor" movies very briefly in "Endgame," when Thor and Rocket go back in time to retrieve the Aether Infinity Stone.

The two Avengers' time-travel journey brings them to Asgard at the same time Foster (Portman) is on the planet during the events of 2013's "Thor: The Dark World." In one scene, we see Thor (Chris Hemsworth) and Rocket (voiced by Bradley Cooper) sneak past Loki (Tom Hiddleston) while he's a prisoner in a cell. Later, we see a shot of Foster before Rocket successfully gets the Aether out of her off camera (earlier in "The Dark World," Foster was infected by the Aether).

According to "Endgame" coeditor Jeffrey Ford, both shots were from unused footage from "The Dark World."

"The shot of Loki throwing his cup in the cell and Thor and Rocket sneak past him in the background, that's a piece of digital negative taken from the dailies of 'The Dark World' that we repurposed," Ford told Business Insider. "The same for the scene of Natalie Portman."

Read more: "Avengers: Endgame" editor reveals how Black Widow's huge scene was dramatically changed

"Endgame" codirector Anthony Russo said in an interview with Entertainment Weekly that Portman did "a little bit of voice-over when she's talking in the distance," but that was the only thing she had to do for the movie. Heck, the line is so brief and faintly placed in the background it wouldn't be a shock if she didn't have to show up to the edit suite to do it. She might have just delivered the line from her phone and sent it to the team.

"Avengers: Endgame" is currently playing in theaters.