Kaley Cuoco and Johnny Galecki’s reunion created a big bang online.

The actors appear in an ad for the video game Royal Kingdom together, six years after the finale of their CBS sitcom “The Big Bang Theory.”

The series followed best friends, roommates, and physicists Sheldon Cooper (Jim Parsons), Leonard Hofstadter (Galecki), and Howard Wolowitz (Simon Helberg).

Galecki’s Leonard married Cuoco’s Penny, with the on-screen couple tying the knot twice on the show.

First, the couple exchanged vows in a Las Vegas elopement during the Season 9 premiere before having a second wedding ceremony with friends and family in Season 10.

Cuoco and Galecki also dated in real life from 2008 to 2010 after meeting on set.

Cuoco, 39, shared the commercial on her social media platform, captioning the Instagram video: “This was so fun to shoot! Back together with my buddy JG.”

The clip starts by showing the “Based on a True Story” star sorting through board games to play as she says, “Okay, ready for game night!”

But the “Roseanne” alum, 49, quickly cuts her off, having an idea of his own to share.

He then comes into the room holding up his phone to showcase the app.

“Royal Kingdom is a brand-new puzzle game that just launched,” he says. “So we don’t need these.”

“Wait, what?” Cuoco asks as Galecki takes the games off the table and tosses them out the window.

“Hey! Those are my games,” shouts “The Flight Attendant” actress before Galecki explains, “I told you, all we need is Royal Kingdom. You can build kingdoms by solving puzzles.”

Once Galecki hands Cuoco his phone, she’s hooked. The camera pans to a close-up of her phone as she exclaims, “Oh wow! That is fun.”

The “8 Simple Rules” vet then tosses more games out the window before Galecki tells her the app is free.

“Was that an overreaction?” she ponders to her former co-star. “Maybe,” Galecki simply states.

The two stare out the window as the actor justifies, “But this game is awesome.”

“Can we play the game now?” Cuoco says as she and Galecki pull out their phones and start playing.

Fans flocked to the comments section to share their excitement over the mini-reunion.