The performance was a "full circle" moment for Musgraves, who performed the song at 9-years old.
"Rainbow Connection" was written by Paul Williams and Kenneth Ascher for the 1979 film The Muppet Movie. The song, originally performed by Kermit the Frog (voiced by Jim Henson), has been covered multiple times throughout the years. Nelson recorded the song for his 2001 album Rainbow Connection.
The pairing was part of several collaborations during Country Music's Biggest Night. Other special collaborations included Garth Brooks and Blake Shelton, Brooks & Dunn and Brothers Osborne and Lady Antebellum with pop artist Halsey.
Previous 2019 CMA performances included Miranda Lambert, Reba McEntire, Keith Urban, Carrie Underwood, Maren Morris, Luke Combs and Eric Church. Dolly Parton performed with For King & Country and Zach Williams, while Chris Stapleton shared the stage with Pink.
Nelson and Musgraves previously collaborated on the duet "Are You Sure?," which was featured on Musgraves' sophomore album Pageant Material and "A Willie Nice Christmas" from Musgraves' holiday album A Very Kacey Christmas.
Musgraves won Female Vocalist of the Year at this year's CMA Awards. She was nominated alongside Kelsea Ballerini, Miranda Lambert, Maren Morris and Carrie Underwood. She also earned a Song of the Year nomination for "Rainbow," along with co-writers Natalie Hemby and Shane McAnally.