kurt and blaine sang baby, it's cold outside at the royal albert hall in october. i need to lie down.

Photo: Darren Criss on the Glee Live tour in 2011. Rach, CC BY 2.0, via Wikimedia Commons

via Billboard, QNews and a fan's video of the show

"I'm gonna do my best to sing both parts," Darren Criss told the Royal Albert Hall on Sunday, per Billboard, and launched into "Baby, It's Cold Outside" alone. Which is a lot to ask of anyone, and a war crime to ask of a room full of people who owned Glee Live T-shirts.

A few lines in, the crowd started screaming. Chris Colfer had walked onstage.

"Hey, Darren!" he said, Billboard reported. In a fan's video, you can hear the rest: the only thing inappropriate, Colfer tells him, is "doing it without me." Then the two of them introduce themselves like it is 2010 again ("I'm Chris." "I'm Darren."), Criss says "It's been a while," Colfer says "It has," and they sing the song, both parts, together.

why this one hits

For the young people: "Baby, It's Cold Outside" was Kurt and Blaine's duet in Glee's 2010 episode "A Very Glee Christmas," and it peaked at No. 57 on the Billboard Hot 100. A lot of us were gay kids watching Fox at the time, and we remember exactly where we were.

It was Criss's first time headlining the Royal Albert Hall, across two back-to-back shows on Sunday, and he packed the night with friends. Billboard lists Alan Cumming on "Does Your Mother Know," Sarah Hyland on "Suddenly Seymour," Jesse Tyler Ferguson, Gaten Matarazzo, and Alex Newell and Andrew Barth Feldman among the guests, before a youth choir joined him for "Somewhere Only We Know" and "Teenage Dream" to close. Subtle, he is not.

is this about the reboot?

Nobody onstage said so. But the timing is rude. Last month Ryan Murphy said he had finished a Glee reboot script, and QNews notes Colfer told Bustle at the time that he knew nothing and had heard absolutely nothing. He may still know nothing. He does still know the words.

The next day Colfer posted: "What a night! I'll never forget it as long as I live." Same, babe. Same.