The husbands-to-be and dads to twins Harper and Gideon head to Las Vegas, baby!
So what were two handsome fellas up to earlier this week in Sin City?
The How I Met Your Mother funnyman was referring to The Rocket Man's new show, Million Dollar Piano, at the Colisseum at Caesar's Palace. The couple watched John perform classics like "Bennie and the Jets" and "Circle of Life."
"Elton's show was f***ing unreal! He's fanfriggingtastic. If you go to Vegas... See. This. Show," Harris tweeted after the 90-plus minute concert. Burtka tweeted, "Amazing!" along with a photo of John performing in gold sequined jacket.
They also hit the überprivate post-show soiree at Central Michel Richard, where guests enjoyed fried chicken and smashed potatoes and mini beef and lobster burgers. Sir Elton John was in a "very good mood" and chatted and mingled with friends. The party died down at about midnight.
They may be besties, but maybe John is also considering Harris for his upcoming biopic?
That's not the only celeb sighting we have for you today...
Jon Hamm drank beers with pals and enjoyed live music at Harvard and Stone in Hollywood.
Sarah Michelle Gellar hit West Hollywood's Andy Lecompte salon for some Joico hair treatments.
Karina Smirnoff played some poker with fellow DWTS pro Peta Murgatroyd at the Get Lucky for Lupus charity benefit in L.A.
Grey's Anatomy star Kevin McKidd stopped by Jeremy Kenyon Locker Corbell's Bunraku Art Experience event at the Chateau Marmont in West Hollywood.
Coming up, Zoe Saldana will host Gen Art's Annual Fresh Faces in Fashion event presented by Moraccan Oil on Oct. 22 at Vibiana in dowtown L.A.