NCIS Scoop: Lily Tomlin Reveals that McGee's Grandmother Is a [Spoiler]!

If you’re an NCIS fan, you already know that iconic funny lady Lily Tomlin will be guest-starring this coming season as McGee’s grandmother. But what you may not know is that Penelope McGee, akin to her kin, is a science nerd.

“She’s a scientist, and she’s very sharp,” Tomlin told TVLine after the Television Critics Association panel for the Showtime series Web Therapy (Tuesdays at 11/10c), on which she guest stars.

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Further describing Penelope, Tomlin said, “She was an admiral’s wife for many decades, and she’s the mother of McGee’s father…. It was a really good part, and I was really delighted to get it.”

NCIS showrunner Gary Glasberg told me that Tomlin figures into a “really fun, big, McGee-centric episode,” one that is not just about family but has a procedural aspect as well.

“We’re really happy with her,” he said of the Laugh-In alumna’s casting, “and I hope that maybe we can get her to come back.”

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Have McGee and his grandma been close over the years? Or does the procedural aspect of the episode manage to bring together two estranged family members? “They’re a military family, and they’re very science-minded, so they’re not overly emotional,” Tomlin says. “But we have this opportunity [to change that].”

Tomlin hails her TV grandson, Sean Murray, as “so darling, he kills me!” As the events of the episode play out, Tim McGee will experience a “kind of a breakthrough,” she says. “[Penelope] makes a connection with him, and we both come to a new place.”