Fourteen-year-old Saints super fan Jarrius Robertson, who is battling biliary atresia -- a chronic liver disease which affects physical growth - is surprised by coach Sean Payton, who invites Robertson to Sunday's game as an honorary team member. (1:34)

The New Orleans Saints on Tuesday signed Jarrius Robertson to be their "hype man" for Sunday's game against the Kansas City Chiefs.

Who Dat?

Robertson, 14, is a Saints super fan. He also is battling biliary atresia -- a chronic liver disease which affects his physical growth -- and has been in and out of hospitals since receiving a liver transplant when he was 1. He now needs another and is on the waiting list. He has had 13 surgeries, and at one point was in a coma for an entire year.

WATCH: "You don't have to tell me twice!" @Saints superfan @Jarrius gets signed LIVE in Times Square! https://t.co/pYW0XkKire — Good Morning America (@GMA) October 18, 2016

Robertson's attitude has made a lasting impression on the Saints since players met him last December at Ochsner Hospital For Children in New Orleans. During that visit, he gave defensive players instructions and told players to "tell Sean Payton you got a new defensive coordinator!" shortly after Rob Ryan was fired.

Robertson, who often attends practices or games and provides constructive criticism, then began doing videos with the team, including one where he comically told soft-spoken receiver Marques Colston to stop "trying to be Mr. Show-Off."

"As a coach, you love it when you see someone with his energy," Saints coach Sean Payton said during an appearance on ABC's "Good Morning America" on Tuesday. "He is on everyone's butt, trust me."

Payton, quarterback Drew Brees and defensive end Cameron Jordan appeared on "Good Morning America" to surprise Robertson by making him an "honorary member" of the team.

Robertson, who was presented with a contract, will fly with the team to Kansas City along with his father for Sunday's game against the Chiefs and will serve as the Saints' social media reporter for the game.

Said Robertson, who quickly signed the contract: "You don't have to tell me twice!"

ESPN Staff Writer Mike Triplett and ABC News contributed to this report.