In the clip, Keaton jokingly shades Reynolds by calling him "Mr. Lively," but the star says he's got no problem with that whatsoever.
"Oh, I'm Mr. Lively 24/7," Reynolds told ET's Carly Steel at the premiere of Deadpool 2 in New York City on Thursday, where he and Lively walked the carpet. "And I'm happy about it. It's great. [It's the] best gig."
The cute pair stunned on the red carpet, where Lively paid tribute to Deadpool himself, rocking the Merc With the Mouth's signature color scheme of red and black.
Reynolds gushed over how well she "rocked" the look, and admitted that he would have done the same for her if she was playing the profane anti-hero.
"If she were Gwenpool I'd be wearing the Deadpool colors as well," Reynolds said, referring to a somewhat obscure character from Deadpool's comic book lore.
Over the weekend, Reynolds appeared on a regional South Korean reality singing competition show called King of Masked Singer, where he donned a glittery unicorn outfit to perform a rendition of "Tomorrow" from the musical Annie.
While Reynolds admitted that he didn't run the idea past his wife first, he said, "She knows how terrified I am of singing in public, so yeah, if I had told her I think she would've pushed me to do it. Because I am terrified of singing."
All of his recent promotional stunts -- from appearing on an Italian version of Dancing With the Stars to filming Twitter videos in full Deadpool costume while lying in Hugh Jackman's hotel room bed -- have all been a part of a carefully and hilariously crafted campaign to showcase the wonderful strangeness of Deadpool 2 -- a film and franchise that exists almost entirely because of Reynold's tenacity to get it made.