Even on LSD, Roger Sterling probably couldn’t have envisioned this: John Slattery is joining the cast of Arrested Development.

TVLine has learned exclusively that the Mad Men actor will appear in multiple episodes of the cult comedy’s upcoming 10-episode Netflix resurrection.

But who is he playing?! That’s the $1 million question. A rep for the show declined to comment, which leaves us no other choice but to speculate. Is he a long-lost Bluth relative? Lindsay’s new side dish? (Hit the comments with your own theories.)

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In an interview with MTV.com, AD exec producer Ron Howard indicated that several new characters would be introduced, although he declined to provide specifics. “[Series creator] Mitch [Hurwitz] isn’t trying to recreate something,” Howard told the site. “It’s been away for a while, and part of the fun that Mitch has been mining and exploiting is, what’s new to discover about these people? What’s delightfully unchanged? He and the writing staff and the actors have a fantastic sense of that. They’re pretty brazen, pretty bold and fearless. That’s what made the show into something that fans really kept alive.”

As previously reported, all 10 new Season 4 episodes of Arrested Development will be released at once, sometime next year on Netflix.