Pratt strolls out onto stage wearing a denim jacket with a design of Stapleton's face on the back of it, as seen on the singer's latest album From a Room: Volume 1.
Before duetting with Stapleton for the David Allen Coe cover "Tennessee Whiskey," Pratt made sure to show off his new threads, thank Chris and his wife Morgane and give his well wishes to the men and women in the armed forces.
"What's Up Nashville?" Pratt said. "I've got this awesome jacket. It's got your (Chris') face on it...I just want to say a special thank you to Chris, to Morgane, to the men and women overseas serving our country."
Pratt then flexes the vocal muscles he's touched on in Guardians of the Galaxy and Parks and Recreation.
At the end of the jam, he embraces both Chris and Morgane before the trio leaves the stage. Stapleton then returned for a three-song encore.
It's unclear if Pratt was in Nashville on business or if he was simply enjoying a visit to Music City.
The show was the second of two back-to-back performances for Stapleton at Bridgetone Arena.
This wasn't the first time Stapleton has brought up an unexpected guest to one of of his shows. He recently reunited with Justin Timberlake for a performance at the Pilgrimage Music Festival in Franklin, Tennessee.