As you know, in Star Trek Beyond, Sulu will be revealed to be gay. This is good! It's progressive, it makes the cast more diverse, and it puts an LGBTQ character in a heroic role. Most fans are OK with this decision (with one exception being, uh, George Takei?). The only beef seems to be the sudden change to the Star Trek canon. After all, this is the third film in the reboot. Why not introduce Sulu as gay in 2009?
Then again, Trek has a long history of giving characters sudden, sometimes baffling backstories, often to provide drama for just one episode...but which then became part of the canon for all time. Here are some of the most strange or most annoying, with one "good" exception at the end. If you can think of others, put 'em in the comments.
Tasha Yar Has a Sister
Apparently no one was happy about Tasha dying, which allowed actress Denise Crosby to leave the show in the first season. So the writers gave her a sister, Ishara, to allow the characters to address their comrade's death. Instead, everyone just wanted her to act more like Tasha... which drove Ishara crazy, since she resented Tasha for abandoning her. The crew may have gotten some closure from Ishara, but she just went back to her doomed planet and was never heard from again.
Spock Has a Half-Brother
Star Trek V was bad enough, but this particular plot made very little sense. Sybok, the film's villain, turns out to have the same father as Spock, but a different mother. Kirk even mentions in the movie itself that he has never heard of this. Does Spock use his intimate knowledge of Sybok, learned from their childhood together, to outsmart the villain and save the day? Nope. Sybok was just Spock's half-brother because why not?
Riker Has a Clone
The Enterprise returns to a planet where Riker was stationed eight years ago and discovers another version of Riker still living there (because of atmospheric distortions during transporting or somesuch). This was Thomas Riker, who turned a ridiculous hand-waving idea into something intriguing. This Riker was still in love with Troi, this Riker was still a hothead. This Riker didn't like what the "real" Riker had become. Eventually, he left the Enterprise and turned up on Deep Space Nine as a Maquis terrorist and (sympathetic) villain. He offered an interesting glimpse into a main character's personality, unlike a certain Vulcan half-brother.
Dr. Bashir is Enhanced
This really made no sense. In the fifth season of Deep Space Nine, Dr. Bashir discovered—along with the rest of us—that his parents had him secretly genetically enhanced when he was a teenager. The character was shocked, and actor Alexander Siddig was not happy about the change, worrying he was supposed to act like Data from then on. Bashir had to admit to O'Brien that he was deliberately missing the bullseye during their dart games, which undercut all their friendly conversations around the dartboard. Bashir was already brilliant but flawed; what did this revelation add to the character?
Trip's Sister is Killed by Terrorists
You could argue that all of Star Trek: Enterprise was one long, unnecessary backstory. One of the more misguided moments of the series was to invoke September 11 with an unprovoked alien attack on Florida. Among the casualties was Trip's sister, and he was deeply affected by it. The audience might have been, too, if she hadn't only been briefly mentioned—but never seen—in two episodes before her death. We finally got a glimpse of her in a dream sequence after the attack, looking pretty and drinking a 22nd-century milkshake. Trip went on to become bitter and vengeful, and his grief and recovery became a major character arc. But it was all over someone the audience barely knew.
Kirk Has a Girlfriend
In Star Trek Generations, the Nexus lets you live out your fantasies... and also travel in time (yes, it's a horrible concept. Let's move on). When Kirk enters the Nexus, we see that his fantasy involves chopping wood, making eggs, and riding horses. It also involves Antonia, a woman he loved, but then left to go back to Starfleet. That's because, just two films earlier, when McCoy says "Other people have families," Kirk replies, "Other people, Bones. Not us." Well, you can forget that poignant moment, because apparently Kirk wanted a family all along! But then decides not to have one and leave the Nexus with Picard. Ugh.
Picard Has a Son
...except he doesn't. It was all a trick by a Ferengi, hoping to avenge the death of his own son at Picard's hands. But wouldn't it have been cool if Picard had a son? And that son was ever, ever heard from again in any episode or novel? Guess we'll never know!
Troi Has a Sister
Yes, it seems everyone gets a sister on Star Trek. But this is one time it actually worked. When Troi's mother collapses, Deanna has to enter her mind and discover what traumatic event caused her illness. It turns out that Troi had an older sister, whom she never knew about, who had drowned when Troi was a baby. Lwaxana was shattered by the accident, blamed herself, and erased all evidence of the sister's existence—an explanation that makes more sense then most of the entries above. It's a powerful episode, well-played by both actresses, as their characters bond over the shared loss. Hopefully the new Trek will handle Sulu's sexuality with this kind of thoughtfulness and meaning. Or maybe Sulu's personal life doesn't need any justification.
Just as long as no one has a secret half-brother.