Hader opened up to ET at the season four premiere screening of 'Barry' at Hollywood Forever on Sunday.
Hader walked the carpet at the premiere screening of Barry season 4 on Sunday, held at Hollywood Forever, and he spoke with ET's Denny Directo about the surprising way he found out about his unexpected bond with Burnett -- which she discovered while appearing on a recent episode of Finding Your Roots.
"She emailed me," Hader said with a laugh. "Yeah, she emailed me and said, 'Hey, we're related.' And I went, 'What?'"
"I told my my, kids! I'm like, 'We're all related to Ms. Hannigan," and they were like, 'Ah!!'" Hader added, referring to Burnett's iconic role in Annie. "So it was really fun."
As it turns out, he and Burnett have been keeping in touch ever since, as Hader explained, "We've been texting and emailing and and stuff, so it's been really exciting. I hope I can, like, have dinner with her."
Amid that exciting development, Hader has also been gearing up for the final season of his hit dark comedy Barry, and the actor admits that it "feels good" to get some closure on the story and bring it to a satisfying conclusion.
"It's nice to write, you know, 'The End' on the thing, but it's it's going to be sad to say bye to everybody," he shared. "That's the hardest part of it."
Biding farewell to his colleagues will seemingly be much more difficult than leaving behind the character of Barry himself.
"I'm very happy to not have to play this guy anymore," Hader admitted. "He's a very dark character, so I'm happy that that's kind of over with... I'm going to do something very light now."
As for what to expect from the final season, Hader shared, "I think it's funny! Everybody likes to say it's dark, but I think it's really funny."
"I just hope people were entertained, that's all you can really do," Hader said of what he hopes the show's legacy will be. "Everything else is for other people to decide. I just hope you're entertained."
The fourth and final season of Barry premieres Sunday, April 16 at 10 p.m. ET/PT on HBO.