Adam Nimoy appears on tonight episode (5-November-2015) of The Big Bang Theory: The Spock Resonance. Adam Nimoy interviews Sheldon for a Star Trek documentary on how Spock influenced the life of Star Trek fans.

There are pictures of Adam Nimoy on the show on his credits page:
http://www.imdb.com/media/rm1760813824/nm0632382
http://www.imdb.com/media/rm1928585984/nm0632382
http://www.imdb.com/media/rm2146689792/nm0632382
http://www.imdb.com/media/rm2129912576/nm0632382

... and on the page for the episode:
http://www.imdb.com/media/rm1760813824/tt5073156
http://www.imdb.com/media/rm1928585984/tt5073156
http://www.imdb.com/media/rm2146689792/tt5073156
http://www.imdb.com/media/rm2129912576/tt5073156

Mr. Nimoy directed Z'ha'dum (1996) and Passing Through Gethsemane (1995).