Back On? Hilary Duff and Mike Comrie Go Hand-in-Hand to Halloween Party

Talk about friendly exes.

Hilary Duff, 27, and her ex Mike Comrie, 33, were snapped walking hand-in-hand to the Casamigos Annual Halloween Party in Los Angeles Friday night, despite having separated in January after three years of marriage.

Dressed as a tooth fairy in a silver sequin skirt, a white tank top and accessorizing with sparkly wings and a crown, the All About You singer was all smiles next to a handsome Comrie in a tuxedo.

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The two were also snapped escorting their two-year-old son Luca to a Halloween party together last Sunday.

In July, Duff talked to Billboard about their complicated relationship.

"I'm separated from my husband right now, which has been a very difficult thing to go through, but we have a lot of love for each other and we have this beautiful baby," she said.

She also revealed that the couple's split inspired a song on her new album.

"[There's a song] about my separation and my love for this person, that maybe we're not meant to be together, or maybe we are. It's very, very personal," she shared.

But we know at least one person who probably won't be too happy to see these cozy costume party pics -- Hilary's childhood sweetheart Aaron Carter, who admitted to ET in April that he was not going to give up on "the love of his life."

Ever.

"Ugh! I don't know!" a clearly embarrassed Duff said about Carter's cringe-worthy openness during her appearance on Watch What Happens Live! earlier this month. "I don't know what to say about it! It was so many years ago. I literally haven't seen him in… so, it's uncomfortable."

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Check out Aaron's now infamous declaration of love in the video below.