For more than five decades, William Shatner has been entertaining the masses with his portrayal of Captain James T. Kirk on "Star Trek" -- a role with which he's become almost synonymous. But there's something that's been bothering him for a long time, now, and he's finally had enough: so-called "super-shippers," people who believe that two actors on a show are dating "in real life," and who thus take their obsession with the characters and the actors to a dangerous level.

William Shatner: 'My PR woman got a death threat'

In the "Outlander" fandom, "super-shippers" are those who believe that the two leading stars -- Sam Heughan, who plays Jamie Fraser, and Caitriona Balfe, who plays Claire Fraser -- are dating, and go to extreme measures to prove that this is so.

Even though, in many interviews, both Heughan and Balfe have confirmed that they are dating other people, that hasn't stopped the "super-shippers" from taking extreme measures to confirm that the two stars are, in fact, dating. In addition to harassing journalists, fans of the show, the crew of the show, and even the other cast members themselves, they've even gone so far as to threaten William Shatner, and his employees, with harm.

William Shatner explained as much on Twitter.

But it isn't just "Outlander" super-shippers that William Shatner has called out.

"Supernatural," which is a show focused on two brothers who hunt ghosts, goblins, and other, well, supernatural beings, also has a ship of its own, called the Dean/Castiel ship. This is a ship that believes that Dean Winchester -- played by Jensen Ackles -- and Castiel -- played by Misha Collins -- are also in a romantic or otherwise sexual relationship.

William Shatner explained how extreme these shippers can get, as well, on his Twitter.

But Shatner -- who is friends with "Outlander" star Sam Heughan -- said that while it's okay to ship fictional characters, it's a different story altogether when the line between fantasy and reality is blurred.

William Shatner will be performing in Branson, MO, this October.