12/13/2012 04:10 pm ET

Ashley Benson To Guest Star On 'How I Met Your Mother' And More Casting News

Ashley Benson is set to visit "How I Met Your Mother" when the show returns after the winter hiatus. CBS tweeted the news, which teases that the "Pretty Little Liars" star will appear as Barney's "????" in the January 21 episode:

Since she's a little too young to be one of Barney's flames (and our suited hero is still in love with Robin), we're guessing that Benson might be playing Mr. Stinson's long-lost sister. Start speculating now!

In other casting news ...

Sofia Vergara's sister heads to "CSI." Yes, fellas, there's two of them. Sandra Vergara will guest-star as Silvana, a Latin pop star who is about to make her US debut in Vegas when her sister is murdered. [TV Line]

"NYPD Blue" alum visits "Castle." Gail O'Grady will play Margo Cowan, a reality star featured in a "Real Housewives" style series alongside previously announced Gina Torres. [TV Guide]

Billy Campbell Leaves "The Killing." The actor, who played Mayor Darren Richmond in the AMC drama's first two seasons, will not reappear in Season 3. Nor will Brent Sexton and Michelle Forbes. [Variety]

"Newsroom" star joins Rebel Wilson's new comedy. Kelen Coleman has boarded the ABC comedy "Super Fun Night" as a "successful professional who serves as a role-model" for Wilson's nerdy character. [TV Line]

How I Met Your Mother