This isn't much of a surprise, but a treat for 'How I Met Your Mother' fans nonetheless: after missing out on the 'Dexter' Comic-Con 2013 panel a few weeks ago, iconic actor John Lithgow has firmly RSVPed to at least a final season of one show. The former '3rd Rock From the Sun' star will return to 'How I Met Your Mother' in his role as Barney's biological father Jerry Whitaker, but how lengthy a stay will it be?

Much with 'How I Met Your Mother' season 9's other guest stars, Lithgow has only been confirmed for a single episode, likely to attend the wedding festivities of his son and Robin ('Agents of S.H.I.E.L.D.' star Cobie Smulders), but the final season format leaves ample room for the actor to recur over the course of the year.

So far, the final season of ‘How I Met Your Mother’ has recruited such guest stars as ‘Revenge' star Roger Bart, ‘The Office‘ star Ellie Kemper, Sherri Shepherd and Wayne Brady reprising his role as Barney’s half-brother James Stinson. In addition to the most recent clarifications on the final season’s wedding weekend format, CBS also revealed that all four regulars would meet the mother (Cristin Milioti, herself a newly minted regular) prior to Ted.

We'll keep you up to date on the star-studded guest list for 'How I Met Your Mother''s ninth and final season, but what say you? Are you happy to see Lithgow return to the series for the first time since 2011? What other 'HIMYM' alum would you like to see RSVP?

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