It was a horror face-off Sunday afternoon when the casts of Scream Queensand American Horror Story: Hotel came together in Hall H.

Scream Queens is about a sorority at fictional Wallace University plagued by a serial killer seeking vengeance. Hotel is the fifth installment of Ryan Murphy's American Horror Story franchise, this time taking place in a hotel in Los Angeles in 1935.

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The panelists included executive producer and creator for both shows Ryan Murphy, Scream Queens cast members Jamie Lee Curtis, Emma Roberts, Lea Michele, Skyler Samuels, Abigail Breslin, Billie Catherine Lourd, and Keke Palmer and American Horror Story: Freak Show and American Horror Story: Hotel cast members Kathy Bates, Angela Bassett, Sarah Paulson, Evan Peters, and Matt Bomer.

After watching a recap of Freak Show and a preview of Scream Queens, Murphy explained where the idea of Scream Queens came from.

"[Co-creator Brad Falchuk] and I were talking around Season 3 of Horror Story, when we were doing Coven," Murphy said. "We were talking about how much we loved writing some of the comedy of that, particularly Emma's stuff. Two years later we had another conversation about, what if we do something that's a little more network-oriented but keeps that horror vibe alive?" He said ultimately they decided on making a show that would be "Halloween-meets-Heathers."

But none of it would have happened without the original Scream Queen herself. Murphy said if Curtis hadn't agreed to do the show, they wouldn't have made it. Fortunately, she was on board, which gave Murphy a springboard for bringing in other big names. Michele said Murphy called her up and said, "New show, Emma Roberts, Jamie Lee Curtis, neck brace; are you in?'"

Some more highlights:

The killer is in the first episode Murphy said the cast doesn't know which of them is the serial killer, but you'll meet him or her in the first episode. He said that when you look back at the premiere, it will be obvious who the murderer is — a revelation that prompted the rest of the panel to go, "Whaaaat?"

Jamie Lee Curtis has a sex scene! "I wanted to see Jamie Lee Curtis have a sex scene with an 18-year-old," Murphy said. "I wanted her to be powerful and large and in charge and that's what we did."

Lea Michele is getting Snapchat An audience member asked when she was joining the social network, and she said her account will kick off the same day as the show — Sept. 22.

Watch for a horror movie throwback Curtis said in Episode 2, she does a brief "wordless homage" to Halloween.

See shirtless Nick Jonas in the new Scream Queens trailer

Then the conversation turned to Hotel. Obviously, one of the biggest changes to the cast this year will be Lady Gaga. Stack asked Murphy how he scored her for the show. It turns out, she came to him.

"She wrote and said, 'I love the show; would you consider putting me in?'" Murphy said. "And I said yes — in all caps." Gaga said she wanted to play someone evil. Murphy bounced ideas around in the writer's room and came back to her with an offer, which she accepted.

He declined to say who the musical superstar will play, but let some of the other actors give their characters' names: Bomer will play Donovan, Peters is Mr. March, Bates is hotel owner Iris, Bassett is Ramona, and Paulson is Hypodermic Sally.

More things to look forward to:

Matt Bomer in his underwear The actor, who filmed a sex scene for Freak Show in his underwear, filmed his first scene for Hotel — also in his skivvies.

Don't hold out hope for a musical episode "Never say never," Murphy said, but he also says he got that urge out of his system in Freak Show. "The fun of it every year is doing something different for me."

Ryan Murphy says Lady Gaga's role is 'bananas good' on Hotel

Jessica Lange is gone... for now When discussing how he chooses actors he likes to work with, Murphy said he liked that he could change the Horror Story cast from year to year. Some people leave after one season, and some people "go off for a year and then come back, like Jessica Lange," Murphy said, prompting Bassett to lean into her mic and go, "Oh sh--!"

Everything is connected, and there is an endgame A fan asked about Pepper, a character who made appearances in both Freak Show and Asylum. "We have a long-term plan with the show and things are connected, Murphy explained. "This season you'll see more and more of that. Characters from other seasons will check into the hotel. It's part of a connected universe, which I think a pretty cool thesis statement at the end of the run."

Scream Queens debuts with a two-hour premiere at 9/8c on Sept. 22 on Fox.

American Horror Story: Hotel premieres this October on FX.

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