As far as my research indicates, excluding presidents, no famous people have ever come forward claiming to have seen Aliens.
However, some stars and personalities have claimed to have had contact or seen a UFO.
In truth though, this makes sense.
People who see UFOs remain relatively innocent, and seem quirky.
Hunting for UFOs is far more respected than claiming to be in communion with Alien beings.
If a celebrity claimed to have seen or communicated with Aliens, there career would take something of a nose-dive.
Thus, it is in the best interest of a famous personality to keep such reports under wrap.
However, there are more than a few who take an above-average interest in UFO Research, to include Spielberg, Akroyd, and even President Ronald Reagan.
Reagan may have had more information than we can account for.
If you look at some of his comments to the UN and other groups, it honestly seems he meant more than he was saying.
However, President Clinton was recorded as saying, in Hong Kong, that he wasn't aware of an Alien technology or recovered bodies, only that there is a secret facility near Groom Lake, where military testing goes on.
However, he did feel that maybe some Career Bureaucrat had the job of keeping classified information classified.
But it should be important to note that this attitude makes sense.
An agent in charge of a personality's profile would definitely not want this information getting out, less it ruin his client, and himself.
Thus, there are a statistically a few famous people who have had some experience, but are unwilling to discuss on the matter.