 TV Guide 's 2005 book TV Guide : The Ultimate Resource to Television Programs on DVD highlighted " Mork Goes Erk " as one of three " Classic Episodes " of the first season , including " Mork 's First Christmas " , and " Mork 's Mixed Emotions " . Matthew Tobey of Allmovie wrote that the episode was most notable because of David Letterman 's appearance before he became more well known . Donald Liebenson of Amazon.com also cited David Letterman 's performance as : " an abusive EST @-@ like guru " as one of the more memorable parts of the Season One DVD boxed set , but thought that the highlight of the season was the episode " Mork 's Mixed Emotions . " The Dallas Morning News also praised Letterman 's performance as a " shady motivational speaker , " commenting that the episode was a way for Letterman to hone his " smarminess " before his later work on Late Show with David Letterman . Jonathan Boudreaux of tvdvdreviews.com described Letterman as " a flakey EST @-@ like guru , " and called the episode itself " disjointed . " 
