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I had a fanfic idea once that would cross NCIS with Lily Catherine once.
She would be a guest agent with the name "LC Cooper". Before she leaves at the end she is asked what the LC is for and she says Lily Catherine. Its also mentioned that her father, a retired admiral, is waiting downstairs with her son and husband.
As an epilogue, Gibbs is in his basement working on a new boat when you hear footsteps coming down. It is retired Admiral Thomas Magnum. It turns out the he and Gibbs had 'met' once back in the 80's when Gibbs was a Marine sniper. It occurs in the final season of "Magnum" in the episode "Unfinished Business" where Magnum is going to kill the Vietnamese agent who killed his ex-wife and supposedly his daughter too. The agent is being exchange for a US officer who was listed as MIA in Vietnam. Snipers had been deployed to kill Magnum before he can kill the agent which would wreck the deal. In the end Magnum can't pull the trigger because he had met the daughter of the MIA prisoner who was overjoyed at getting her dad back. He's not going to create the pain he's feeling in another person. Gibbs had had Magnum in his rifle's sight but didn't pull the trigger even though he was under orders to. He just 'knew' Magnum wouldn't do it.
Magnum thanks Gibbs for the chance to reunite with his daughter and watch her grow up, marry, and have a son: Thomas Magnum Cooper. He also understands what Gibbs did when he killed the murder of his wife and daughter.
Goes on from there.