Watch: Sam Richardson discusses comedy, action and his superhero future
The 37-year-old star, best known for his work in TV comedy series like Veep and New Girl, joked to Yahoo Entertainment UK that it was "very financially satisfying" to make the leap to major blockbusters.
He appears in the movie as Charlie, who joins Pratt's character as part of a wave of present-day people conscripted to travel through time in order to fight a future war against a vicious alien race.
"I love action movies and I love sci-fi movies, so to get to be in one in such a prominent, fun, cool role was like a dream for me," said Richardson.
"Also being able to bring my talents and skills that I had previously used and apply them to a genre that I love and revere so much was a perfect gift for me and a perfect opportunity."
Richardson said he would love to do more blockbuster work on the big screen and said he "truly wants to" join Pratt in the Marvel Cinematic Universe.
He said he loved working with the Guardians of the Galaxy actor, given the fact he also made the leap from TV comedy to the biggest possible screens and movies.
"[Pratt] was great as a sounding board and just to play off of," Richardson said.
"Playing alongside a person who has a true comedic background, but he's also a full action star. So there's not a better person to do a movie like this with because he is both, right?
"I get to have a scene partner who understands comedy so well, but I also get to learn from an action star who understands the action genre so well. It was wonderful. It was a cheat code."
As well as Pratt and Richardson, the cast of The Tomorrow War includes GLOW star Betty Gilpin, Yvonne Strahovski and JK Simmons as the estranged father of Pratt's character.
The movie was originally produced by Paramount Pictures, but was sold to Amazon as a result of the COVID-19 pandemic for a reported figure of around $200m (£142m).
The Tomorrow War will be available to stream on Amazon Prime Video from 2 July.
Watch: Trailer for The Tomorrow War