Avengers: Endgame

You were put with Scott (Antman), Tony (Iron Man), Steve (Captain America) and Bruce (Currently merged with Hulk). Tony and Scott were going to retrieve the Space Stone while Steve got the Mind Stone and Bruce got the Time Stone. You were there for backup, just in case things went wrong

Tony: ‘Mr. Rogers, I forgot that suit did nothing for your ass’

Steve: ‘No one asked you to look Tony’

Scott: ‘I think you look great Cap, as far as I’m concerned, that’s America’s Ass’

He’s currently tiny and standing on Tony’s shoulder, doing a salute