James Gunn joined Kaley Cuoco's 'Harley Quinn' after receiving a message on Twitter from one of the show's producers

• Warning: There are minor spoilers ahead for "Harley Quinn" season three, streaming now on HBO Max.
• Director James Gunn surprisingly cameos on the new season as himself.

The wait is over. After more than two years, season three of Kaley Cuoco's underrated gem, "Harley Quinn," is back.

If you tune into the first three episodes of the adult animated series, now streaming on its new home of HBO Max, you'll catch "The Suicide Squad" director James Gunn in an important cameo as the director of a Thomas Wayne biopic.

Teased in the show's trailers, Insider asked the show's executive producers Justin Halpern and Patrick Schumacker over Zoom on Wednesday how Gunn wound up on the new season.

It turns out Twitter played a big role in making the cameo a reality.

"We knew he was a fan of the show," Schumacker told Insider. "He had sort of just, out of the blue, been tweeting about the show, clips, or just thoughts on it — all very positive."

"We knew we were going to be doing this storyline that involved a sort of prestige awards-worthy biopic of Thomas Wayne, kind of 'Aviator'-style," Schumacker continued, saying they were seeking out who may be a great fit for the part of the director.

"We thought of James because, I think it's fair to say, he makes big-budget popcorn movies that are not this. But now this is his transition into... Now he's in his Scorsese period and he's making something a little bit more serious."

There was just one problem. Neither Schumacker nor Halpern knew Gunn. They just knew that he really seemed to enjoy their animated series.

Schumacker took a gamble and reached out to Gunn over Twitter.

It paid off.

"I just DM'ed him because we happened to follow each other, never thinking I would get an answer. We don't really know each other. I've never met him in person," Schumacker said. "What ended up happening was he got back to me almost immediately and was like, "I'm in. Let's do this. Here's my rep's info. Let's make it happen.'"

"Within a few weeks, I got to voice direct him," Schumacker added. "It was remote because he was up in Vancouver shooting 'Peacemaker.' We spent like an hour or so together, remotely, and it was a blast."

Schumacker said they bounced around ideas for meta jokes on Marvel, where Gunn has directed the "Guardians of the Galaxy" franchise, and that Gunn was "a good sport" who even offered up some bits of his own that pushed the envelope a bit more.

"He's a funny improviser," said Schumacker of how game Gunn was for anything. "He could have said no to all this stuff and he didn't. He said yes to all of it... It was like a fish to water in this sort of context for him."

On the season, Gunn's character directs a fictional Billy Bob Thornton (who is voiced by the actor) as Bruce Wayne's father and interacts with Clayface (Alan Tudyk), an aspiring thespian who would do anything for a chance to work with Gunn, even if it means shapeshifting his body into a director's chair to keep him cozy.

"I just really appreciate that he made time to do it because I know 'Peacemaker' was a big undertaking," Schumacker said, adding, "I think he's proud of it 'cause he's changed his Twitter avatar to his Harley cartoon self."

"We'd love to have him back if he's ever around and we end up getting lucky enough to do another season," Schumacker added. "It would be great."

Also starring the voice talents of Lake Bell, Ron Funches, Jason Alexander, and JB Smoove, the first three episodes of "Harley Quinn" are now streaming on HBO Max.