CM Punk is one of many Superstars who has wrestled in a WWE ring as well as a UFC/MMA ring. While the likes of Brock Lesnar and Ronda Rousey - who have been in both rings - had success in both promotions, the same can't be said about Punk.
Punk had a glorious WWE career, but his time in UFC was a massive failure. He has been in two UFC fights and has lost both, but he still appears to have been tested by USADA - United States Anti-Doping Agency, recently, as per Aaron Bronsteter of TSN Sports.
Punk's last fight was back in 2018 and him being in the testing pool is a little baffling, considering how UFC President Dana White said that the former WWE Champion's UFC career was over.
Dana White praised the former WWE Superstar for showing a lot of heart after his loss to Jackson in 2018, but he said that Punk "should call it a wrap" on his UFC career.
“No, it should be a wrap. The guy’s 39 years old. We gave him two shots, and he had a lot of heart tonight, and I think he should call it a wrap.”
Punk has still been involved in MMA as a commentator for Cage Fury Fighting Championships. He also recently returned to the WWE sphere, appearing as an analyst on FOX's WWE Backstage show.