NCIS will welcome Lily Tomlin this upcoming season as McGee’s grandmother.

Not surprisingly, it turns out that Penelope McGee is also a major science nerd.

“She’s a scientist, and she’s very sharp,” Tomlin told TV Line of her character.

“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.”

“They’re a big military family, and they’re very science-minded, so they’re not overly emotional,” Tomlin adds. “But we have this opportunity [to change that].”

Tomlin also says Sean Murray's (“so darling, he kills me!) Tim McGee will experience a “kind of a breakthrough after [Penelope] makes a connection with him.”

NCIS show-runner Gary Glasberg says Tomlin's casting is central to “really fun, big, McGee-centric episode” about family, but with a procedural aspect as well.

“We’re really happy with her,” he said, adding that perhaps this will be more than a one-shot deal for Tomlin. “I hope that maybe we can get her to come back.”

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.