Wil Wheaton
Wil Wheaton played an exaggerated version of himself on The Big Bang Theory. Sheldon was dying to meet the child star on Star Trek, only be woefully disappointed by Wil's attitude. The two had such a rocky start that he briefly became one of Sheldon's enemies.
Will Played Himself
Richard William Wheaton III, otherwise known as Wil Wheaton, was a child actor in Stand by Me and later graduated to a prominent role on Star Trek: The Next Generation as Wesley Crusher. These days, Wheaton does a fair amount of voiceover work. He also hosts a YouTube series called TableTop.