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File this under late night Twitter developments: Pretty Little Liars' Ashley Benson is heading to How I Met Your Mother.

CBS confirms Wednesday's cryptic announcement -- "#PrettyLittleLiars’ @AshBenzo is going to guest star as Barney’s???? on Jan. 21! Suit Up!" -- that the ABC Family star recently taped a guest spot for the comedy's eighth season.

And while the news of a Barney (Neil Patrick Harris) storyline hints that Benson might play one of the lady-killer's many (would-be) conquests, the character isn't technically on the market. Barney, again pushing Robin (Cobie Smulders) to the side, has been dating his ex's nemesis, Patrice (Ellen D. Williams).

Fans won't have to wait long to find out what exactly Benson is doing on the show. After Monday's one-hour Christmas outing (with guest Seth Green), the episode in question will be the second of the new year. That's just two weeks after Pretty Little Liars returns.

Benson is repped by WME.

Getty Images

File this under late night Twitter developments: Pretty Little Liars' Ashley Benson is heading to How I Met Your Mother.

CBS confirms Wednesday's cryptic announcement -- "#PrettyLittleLiars’ @AshBenzo is going to guest star as Barney’s???? on Jan. 21! Suit Up!" -- that the ABC Family star recently taped a guest spot for the comedy's eighth season.

And while the news of a Barney (Neil Patrick Harris) storyline hints that Benson might play one of the lady-killer's many (would-be) conquests, the character isn't technically on the market. Barney, again pushing Robin (Cobie Smulders) to the side, has been dating his ex's nemesis, Patrice (Ellen D. Williams).

Fans won't have to wait long to find out what exactly Benson is doing on the show. After Monday's one-hour Christmas outing (with guest Seth Green), the episode in question will be the second of the new year. That's just two weeks after Pretty Little Liars returns.

Benson is repped by WME.