The 21-year-old television personality and 26-year-old rapper had a family photo shoot Thursday with 14-month-old Stormi before attending an Avengers: Endgame screening for Scott's birthday.
Jenner shared a photo on Instagram of herself with Scott and Stormi. Jenner transformed into Captain Marvel, while Scott and Stormi dressed up as Iron Man and Thor, respectively.
"happy end game everyone," she captioned the post.
The Keeping Up with the Kardashians star followed up with two more pictures of herself with Scott.
"oh you didn't catch iron flame and captain lip kit in the credits? sucks 4 you," she joked in the caption.
Entertainment Tonight said Jenner threw an early birthday party for Scott at a movie theater Thursday in California. Kim Kardashian, Kanye West, Khloe Kardashian, Kourtney Kardashian and Kris Jenner were among the guests in attendance.
Scott, who officially turned 26 on Friday, reacted to Avengers: Endgame in a post Thursday on Instagram Stories.
"Got to Watch avengers today wit da da fam oh my geeze!!!!" he wrote.
Brie Larson, Robert Downey, Jr., and Chris Hemsworth play Captain Marvel, Iron Man and Thor in Avengers: Endgame. The movie officially opened Friday and took home a record $169 million overseas after one day of release.