The night before the event, Halsey appeared to make her relationship with Evan Peters Instagram official

Halsey and Evan Peters are making their romance red carpet official.

On Saturday night, the pair attended the American Horror Story 100th Episode Celebration in Los Angeles together. Their red carpet debut comes just over one month after they were first spotted on a date.

The pair also got into the Halloween spirit by dressing up as Sonny and Cher in a spot-on couple’s costume. Halsey, 25, rocked an asymmetrical rainbow polka dot gown, while Peters, 32, wore a matching polka dot shirt underneath a white suit. The AHS actor even wore a fake mustache and wig to complete the look.

Peters’ ex-fiancée and AHS costar Emma Roberts was also in attendance at the event. The former couple’s engagement ended in March, while Halsey (born Ashley Nicolette Frangipane) recently split from British rocker Yungblud.

Evan Peters and Halsey
| Credit: Axelle/Bauer-Griffin/FilmMagic

On Friday night, just one day before their red carpet debut, the pair made their relationship Instagram official and were seen holding hands after attending Halsey’s Halloween party together.

“Resident goths,” the singer captioned the Instagram post, which shows Peters pointing to Halsey with his hand wrapped around her shoulder. For the festivities, Peters dressed up as a Juggalo — a fan of the group Insane Clown Posse — while Halsey went as Marilyn Manson.

Halsey and Evan Peters
| Credit: BACKGRID

Halsey and Peters were first romantically linked after they were spotted on a date together at Six Flags Magic Mountain in Los Angeles on Sept. 21.

According to an onlooker, Peters appeared to be “flirting” with Halsey as they lined up for the theme park’s Goliath roller coaster.

At around 8 p.m. that evening, the onlooker says the pair hopped onto the ride and held hands tightly as they plummeted down the coaster’s 180-foot slope. A photo of Halsey and Peters — both dressed in gray T-shirts — on the ride shows them smiling as they hold on to the front of their seats.

Halsey, Evan Peters
Halsey; Evan Peters
| Credit: Dimitrios Kambouris/Getty; Kevork Djansezian/NBC/NBCU

According to multiple outlets, Halsey expressed her interest in Peters years ago, reportedly tweeting in 2012, “Seriously Evan Peters stop making me attracted to alleged sociopaths and accused murderers….,” likely in reference to his AHS role.

In since-deleted tweets, Halsey then went on to say, “Petition for Evan Peters to date me” in November 2013 and “I’m a f—ing liar I’m so in love with Evan Peters I’m so whipped I’m whipped as f— !” in November 2014.