In a pair of surprise late spring casting moves at a pair of TV series — one of them TV’s biggest — Wilmer Valderrama will join “NCIS” next fall and John Stamos will join Fox’s “Scream Queens.”

Veteran actor Valderrama, who most recently had an arc on “Grey’s Anatomy,” will play “a once-grounded NCIS field agent who accepted a deep cover assignment years ago and never resurfaced,” according to a CBS news release, which adds, “Many agents don’t know he’s still on the job or that he’s even alive.”

“NCIS” — by far TV’s most viewed drama — lost a core cast member at the end of last season: Michael Weatherly, who will star in a new CBS drama in the fall.

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Miami native Valderrama, 36, has had a long TV career which launched on “That ’70s Show” as Fez, one of the four leads, whose name was essentially an acronym for “Foreign Exchange Student.” (No one knew precisely which country he came from, remember?)

Per “NCIS” showrunner Gary Glasberg, “Fans are going to see him like they’ve never seen him before.”

Meanwhile, Stamos — most recently in “Grandfathered,” which was canceled by Fox after one season — will join “Scream Queens” as Dr. Brock Holt, described as a “secretive head surgeon.” “Scream Queens” was set on a college campus its freshman season and in the fall will relocate to a hospital, “where some of the most fascinating and bizarre medical cases are under observation.”

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Stamos, 52, is one of TV’s best-known and — at least to “Full House” fans — beloved actors (and in fact has a bit role in the Netflix reboot).

Both “NCIS” and “Scream Queens” return in September.