Former World Wrestling Entertainment (WWE) champion Seth Rollins has issued a challenge to CM Punk and called him out for a fight. 

After being away for six long years, CM Punk made an unannounced appearance on Tuesday night's episode of "WWE Backstage", FS1’s new weekly studio show. The two-time WWE champion made a cameo in the show during its final moments with the Living Colour’s “Cult of Personality" being played on the background - Punk's entrance music during his WWE career. 

Although Punk is back working with WWE, his contract is just with FOX Network's WWE Backstage. However, the WWE Universe sees this as Punk's first step toward his return to the ring.

CM Punk CM Punk prepares to fight Mike Jackson in their welterweight bout during the UFC 225: Whittaker v Romero 2 event at the United Center in Chicago, June 9, 2018. Photo: Dylan Buell/Getty Images

"It’s as simple as this: Just when they think they’ve got the answers, I change the culture,” Punk told the camera, before adding, "I’ll see you here next week."

Taking Punk's words seriously, Rollins tweeted to him on Wednesday, "Fight me @CMPunk."

Punk, who left the WWE on bad terms five years back, is also a professional boxer following his loss in the Royal Rumble 2014 match to Batista. For a while, Punk did not talk much about his exit before he finally spoke about it months later in an episode of "Art of Wrestling", hosted by his best friend at the time, Colt Cabana.

Earlier, when WWE Vice President Triple H was asked about Punk's return, the former had insisted that he was open for business with Punk. "That's a 'could be'. Vince will say it all the time: 'We're open for business'. The past is passed, today is today and you never say never in WWE," Triple H had said of Punk's return.

Punk is signed up with the Ultimate Fighting Championship (UFC), where he fights in the welterweight division, and to Cage Fury Fighting Championships (CFFC), where he works as a commentator. Apart from his Mixed Martial Arts (MMA) career, Punk has since his WWE exit also gone on to author comic books for Marvel and more recently, star in the horror film “Girl on the Third Floor.