The Knights teammates will add experience, flair and some mystery to a side well beaten by NSW in Melbourne, coach Billy Slater somewhat forced into changes after injuries to incumbent wingers Xavier Coates and Murray Taulagi.
The shuffle will put Gagai at centre, marking club teammate Bradman Best, and Ponga likely off the bench in a utility role he executed on Origin debut in 2018.
Gagai, 33, played 22-straight Origins before he was cut from last year's squad.
"It did cross my mind whether I'd be able to get the call back," he said.
"It's a jersey you never want to give up, but one you always have to earn.
"The emotions were more excitement and happiness, and to let my boys know I was back in the side.
"That was the hardest thing for me last year, letting them know, because that's all they've known."
Dismissing the narrative that he "steps up" for Queensland, Gagai thinks his club form had spoken for itself.
"I wouldn't say I'm playing with a chip on the shoulder, but a point to prove," he said.
"I'm not as young as I used to be, but Daly's (Cherry-Evans, 35) showing the way, the old fellas have still got it."
Kalyn Ponga will likely be asked to get physical in his State of Origin return. (Dave Hunt/AAP PHOTOS)
Ponga returned from an 11-week lay-off due to a foot injury on Sunday.
"I said to him he might have to warm his shoulders up," Gagai said of Ponga, who would be required to make more tackles than at fullback if he is picked as a bench utility.
"He's just a footy player and everyone saw that last night ... comes back and shows what he's capable of.
"I'm excited to see him back in a Maroon jersey and to play alongside him. I just can't wait."
Ponga missed last year's Origin series due to repeated concussions but finished the year with the Dally M Medal.
"After the year I had, to go through what I went through with the concussions and almost having to retire, it was a nice ending to the year," he said on Monday.
While validating, he said he "never really doubted himself".
"I always wanted to be back in this arena and I was never going to close the door to it, until I get old," the 26-year-old said.
"I wasn't ready mentally and physically for this arena (last year) ... coming back from everything that was going on ... it was the best thing for me.
"I know what this arena takes. I will warm my shoulders up, I will get myself right and be keen to get out there."
