Wil Wheaton was in a deleted scene in Star Trek: Nemesis.
Back in 2002, Wil Wheaton’s character, Wesley Crusher, made a surprise appearance at the wedding of Captain Will Riker and Counselor Deanna Troi. He appeared in a Starfleet dress uniform as a lieutenant and even talked to Captain Picard about how happy he was to be joining the crew of the Titan, the ship Riker was leaving Enterprise to captain. It was a brief moment of less than a minute, but that scene was deleted, and Wesley wasn’t seen again in the movie. Even though the scene can still be seen (see video below), according to Wil Wheaton who spoke at Star Trek: Mission Chicago [via Trekmovie], it is not canon. This comes from an official Star Trek declaration.
"I will also add, because I know this to be true, this is an official Star Trek declaration: the piece of Wesley in Star Trek: Nemesis in the stuff that’s been cut from the movie is not canonical. Very important… The impression that a certain amount of fandom has that Wesley is a lieutenant about to serve on the Titan is not canonical because it was cut from the movie… Which means, that my headcanon, that Wesley as a Traveler is a little bit closer maybe actually being more like what, if anything, the people who do Star Trek might have in mind."
So where does Wil Wheaton think Wesley Crusher is?
Wheaton thinks Wesley continued as a Traveler, and not only that, he became a Time Lord which allowed him to move through time and space. He used this scenario in his mind to explain how Wesley could appear at Riker and Troi’s wedding if the scene had remained in. The actor admits that he has written his own fan fiction about his character so he has given this a lot of thought.
To explain Wesley’s appearance at the wedding, Wheaton said that Wesley, as a Traveler, would know every moment that happens, and he would have wanted to be at the wedding of his friends. But he couldn’t have appeared as a god-like being so showing up as a lieutenant sounded like the one thing that would have made sense as it would make everyone more comfortable.
"“So Wesley really wanted to be at this moment. He knows that this moment happens. He knows every moment that happens. It’s just part of the terrible knowledge that comes with being a Traveler guy, I guess. And Wesley made a choice: How will they expect me to appear? What will make them comfortable? If I show up as a god-being, it’s going make everything weird and make it all about me and I don’t want it to be that. If I just show up as like a lieutenant… that sounds like a thing that would make sense. Sure, let’s do that. But I get to be at the wedding of my very closest friends and family and I get to see them.”"
Since the wedding scene was deleted, however, Wesley’s actual whereabouts remain a mystery. After he left the Enterprise and became a Traveler, he never returned to visit his friends or family. So, in Star Trek canon, Wesley still exists as a Traveler. Maybe he could show up one day in a future episode of one of the Star Trek series. After all, he can travel through time.