Here's what we do know about Green Day's cameo in the upcoming "The Simpsons Movie": It's happening.

That was confirmed to MTV News by both the band's label, Reprise, and a spokesperson for 20th Century Fox studios way back in February, when a trailer for the film — which contained a split-second-long scene depicting Green Day performing on a capsizing stage — first hit the Net. However, just what they're performing and what role they play in the film (which is due July 27) was unknown.

Check out the trailer here — Green Day appear about 20 seconds before the end — but blink and you'll miss 'em.

Almost three months later, nothing has changed: Neither Reprise nor Fox would provide any further information.

Luckily for us, the cast and crew of "The Simpsons" TV show just happened to be throwing a huge party Tuesday night in Los Angeles, in celebration of seminal show's 400th episode. Surely, we figured, someone there would be able to shed some light on the whole Green Day issue ...

"Green Day is in the movie — I will publicly acknowledge that Green Day are in the movie," "Simpsons" creator Matt Groening laughed. "They're really good sports and I think we both honor them and 'Simpson'-ize them. You can take that however you want. They're really nice guys."

(See Groening talk about which celebrities didn't make it into "The Simpsons Movie.")

"I know that Moe yells out obnoxious stuff to Green Day while they're performing. That I remember," Hank Azaria — voice of "Simpsons" mixologist Moe Szyslak and about 46 other characters on the show — added. "He yells out stupid stuff to Green Day. [They don't play] at Moe's Tavern. They perform elsewhere in the movie; they're outside. And the whole crowd turns on them."

Thanks guys! And while the information provided by Groening and Azaria is spotty at best, it's positively encyclopedic compared to what we got from a couple of other "Simpson" regulars. Which means that — just like most Green Day fans — we're gonna have to wait until July to find out.

"No, [I wasn't there the day Green Day recorded]. We've had close to 400 celebrity guest stars on our show, and I've only worked with a handful of them because their schedules are really in demand," Nancy Cartwright, the voice of Bart, said. "It takes about four hours to do the record[ing] for our show, and they have to make it so they come in while we're there. If they can't, they [record] them separately."

"I didn't know [Green Day was in the movie] until you told me," Yeardley Smith, who voices Lisa, added. "So there you go. I will really be the last to know. I just hope I get to go to the premiere."

Check out everything we've got on "The Simpsons Movie."

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