The fabulous cast of How I Met Your Mother came together for a little early St. Patrick's Day party in Hollywood last night sponsored by Jameson. Sadly, their newest costar didn't come for the festivities, but you gotta believe that Miss Britney was still all anyone wanted to talk about. Alyson Hannigan skipped out on the traditional green garb — but Fab's got all the info on her cute look. How much fun would it be to party with NPH, Jason Segel and the gang? Next time, Brit should totally tag along.

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Images include: Alyson Hannigan, Bob Saget, Cobie Smulders, Jason Segel, Neil Patrick Harris