Celebrity Parents Will Arnett Jokes About Why Newborn Son Denny's Nickname Isn't After the Restaurant Chain Will Arnett and girlfriend Alessandra Brawn welcomed baby Denny, their first child together, on May 27 By Jen Juneau Jen Juneau Twitter Jen Juneau is a digital news writer for PEOPLE since 2016. People Editorial Guidelines Published on July 24, 2020 12:40 PM Share Tweet Pin Email Will Arnett is over the Moon(s Over My Hammy) about being a new dad again. During a Thursday night chat with Jimmy Fallon for the host's at-home Tonight Show edition, the LEGO Masters host opened up about his new baby boy Alexander Denison, whom he and girlfriend Alessandra Brawn welcomed on May 27. "We call him Denny," said Arnett, 50. "I know what you're [gonna say] — not after the fast-food chain." "Why not?!" asked Fallon, 45. "Everybody who knows me knows that I'm a fan of the Grand Slam breakfast," replied his guest, joking with a wink of why he hasn't tied the baby boy's moniker to the famed diner, "The price hasn't been right ... yet." Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories. Will Arnett. The Tonight Show Starring Jimmy Fallon Dad and Baby Son Whose "Conversation" Video Went Viral Star in Adorable New Ad for Denny's Baby Denny is the third child for Arnett, who also shares two sons with ex-wife Amy Poehler: Abel James, 10 next month, and Archibald "Archie" William Emerson, 11. "They're super psyched to be big brothers, and it's been crazy. 'Cause obviously the world is upside down right now, so it's been weird anyway," said the BoJack Horseman voice actor. But social distancing with his family amid the ongoing novel coronavirus (COVID-19) crisis has "prepared" Arnett for being at home with a new baby again. "You know what it's like — those first few months of having a baby are kinda like being in quarantine anyway. You're locked down," he told Fallon. "That's how I felt anyway, and then it's just been kinda double that, so it's been okay." Alessandra Brawn and Will Arnett. Amy Sussman/Getty Images RELATED VIDEO: How Well Do YOU Know Celeb Baby Names? Arnett's rep confirmed baby Denny's birth to PEOPLE on June 12. The actor and comedian's new addition was born in Los Angeles. "Denny is home and everyone is doing well," the rep shared. Arnett and Brawn, the former CEO of clothing brand Chapel, reportedly began dating last year and attended the 2019 Creative Arts Emmys together last September. PEOPLE confirmed Brawn's pregnancy in February. She is also mom to son Nash.