CNN  — 

Fans are crossing their fingers that Dr. Jane Foster is returning to save the world once again.

Natalie Portman, who played the beloved scientist and love interest in the first two “Thor” films, appeared at the “Avengers: Endgame” premiere Monday in Los Angeles.

Her unexpected presence has prompted people to speculate that Foster is returning in the fourth and final installment of the Avengers franchise.

Some fans even hypothesized that the the brilliant astrophysicist will be the key to defeating Thanos, the purple supervillain who wiped out half the universe’s population in “Avengers: Infinity War.”

Foster appeared in 2011’s “Thor” and 2013’s “Thor: The Dark World,” but Portman’s character did not return for “Thor: Ragnarok” in 2017. Foster’s name was mentioned in passing by Thor in subsequent Marvel movies, but it’s presumed that the two broke up.

Portman said in 2016 that she was done with the Marvel Cinematic Universe, but hinted that she was open to reprising the role down the road.

“As far as I know, I’m done,” she said. “I mean, I don’t know if maybe one day they’ll ask for an Avengers 7, or whatever.”

We’ll just have to wait and see if Foster makes a surprise comeback when “Avengers: Endgame” opens in theaters on Friday.