David Gerrold wrote "The Trouble With Tribbles," one of the most famous episodes of Star Trek: The Original Series in the 1960s. Thirty years later, when Star Trek: Deep Space Nine revisited that storyline in "Trials and Tribble-ations," the show's producers invited Gerrold to make a cameo appearance as an Enterprise crew member on the re-created original ship. He's visible walking down the corridors of Kirk's starship, and kneeling down, petting a tribble. Mike Sussman, producer on Star Trek: Enterprise, appeared as a dead body in the corridors of the Original Series Starship Defiant in "In A Mirror, Darkly". Coincidentally, Sussman ended up wearing part of the costume that Gerrold had worn in his cameo.