Star Trek celebrity guest Michael McKean playing The Clown in an appearance on a Voyager episode called TheThaw. He's a famous actor.
The top picture is the actor in normal circumstances, and the bottom picture(s) is of the actor in their specific role(s).
6 Pictures from The Thaw
His most famous role is from the movie, This Is Spinal Tap in 1984, as the singer, David St. Hubbins. But, his first famous role was as Lenny in the TV show Laverne and Shirley from 1976-82. He was also in D.A.R.Y.L., Jumpin' Jack Flash, Planes, Trains & Automobiles and Coneheads.
The Thaw -Star Trek: Voyager - 139 (episode # 2.23) -Playing The Clown -He occupied the computer-generated dreamstate of five hibernating survivors of the Kohl settlement in the Delta Quadrant. The system's control computer created their worst fears. The Voyager crew ended up disconnecting the sleepers and saving the surviving ones from the evil clown character.