Alyson Hannigan, How I Met Your Mother

Lily's father is coming to How I Met Your Mother, series creator Carter Bays tells TVGuide.com exclusively.

"We're going to meet Lily's dad later in the season. He hasn't been cast yet," Bays says. "It will sort of explain a lot about Lily: why she is the way she is, why she's kind of a control freak."

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Avid fans will recall that Papa Aldrin was not seen at Lily and Marshall's wedding in Season 2 — and there's a reason for that, Bays says.

"He was not at the wedding. It's a bit of an estranged relationship and he's going to come back into her life," Bays says. "We find out he wasn't the best dad. It's sort of at the root of why Marshall's very gung-ho about having kids and Lily not so much."

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Lily's dad will appear in the season's Thanksgiving episode and Bays says the Mother crew is currently looking at "a lot of people" for the "fun part."

Season 5 of How I Met Your Mother premieres Monday at 8/7c on CBS.

Who do you think should play Lily's dad? And what do you think happened between father and daughter?