Big Bang Theory costars Johnny Galecki and Kaley Cuoco reunite for game night: ‘Just leveled up’

Kaley Cuoco and Johnny Galecki are together again — for an ad.

The former Big Bang Theory costars, who dated off-screen during the show's early seasons, reunited in an advertisement for the Royal Kingdom mobile app. "Game Night with @sanctionedjohnnygalecki just leveled up thanks to @royalkingdom," Cuoco wrote the caption of her Instagram post sharing the ad. "This was so fun to shoot! Back together with my buddy JG," she added in a comment. 

"Game night with @kaleycuoco just got a serious upgrade thanks to @royalkingdom," Galecki wrote in his own post. "I couldn’t believe it when these folks reached out and asked me to vouch for Royal Kingdom because I can HONESTLY tell you I have played over TEN THOUSAND LEVELS of Royal Match and Royal Kingdom is just as amazing. P.S., I will never claim that anything is great unless I truly believe it to be. Give it a try!"

The ad sees Galecki waltz into Cuoco's house, where she has prepared a spread of board games and snacks — only for him to immediately shout out the mobile Royal Kingdom app and toss his costar's board games out of her window. "Those are my games!" Cuoco exclaims.

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Upon making a couple of swipes on Galecki's phone, however, Cuoco is instantly enthralled by the puzzle game. "Oh wow, that is fun, you're right. We don't need these games," she says.

Galecki notes that the game is free, which prompts Cuoco to also toss her credit cards out the window. "Don't need these!"

Galecki also says that the app doesn't require wifi and doesn't have any ads, which inspires Cuoco to chuck her internet router and TV outside, too. "Is that an overreaction?" she asks.

"Maybe," Galecki responds. "But this game is awesome."

Galecki, who portrayed Caltech physicist Leonard Hofstadter on the series, and Cuoco, who played his neighbor Penny on the sitcom, previously reflected on their relationship in the book The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series. 

"I had a very big crush on Johnny early on," Cuoco said in an excerpt from the book, published in Vanity Fair. "We were both dating people at the time, but I only had eyes for Johnny. Then, when I found out he had eyes for me too, I was like, Uh‑oh, this is going to be trouble."

Galecki had no idea about his costar's attraction, though. "I have a healthy ego, but you really have to kind of club me over the head to let me know you're flirting with me," he says. "I had zero idea of any sort of crush before Kaley and I began dating."

The duo's connection solidified while filming a season 1 dream sequence in which Leonard saves Penny in an elevator shaft. "I think we fell a little in love in that elevator shaft," Cuoco recalled.

"We felt something, yeah," Galecki agreed. "I think that was a massive turning point [in our relationship]. At that point, both she and I knew that something mutual was felt, and that it was going to be more of a distraction from the work to try and continue to ignore it than to actually recognize it and surrender to it."

The former costars still remain on good terms despite ending their relationship around 2010. "He was front row at both of my weddings, and we've been so supportive of each other ever since," Cuoco said, referring to her marriages to Ryan Sweeting and Karl Cook. "We adore each other." 

Galecki agreed: "We continue to love one another, just in other ways."