Cathy (found animated specials based on comic strip series; 1987-1989)
Cathy, Cathy's Last Resort and Cathy's Valentine are three animated specials that aired in 1987, 1988 and 1989, based on the comic strip Cathy by Cathy Guisewite and produced by Bill Melendez and Lee Mendelson, known for producing the Peanuts specials.
Although they received critical acclaim and the first special won Guisewite an Emmy for Outstanding Animated Program, these specials have never been broadcast again since their first years, let alone released on VHS or DVD.
While the first special has been uploaded onto YouTube in two different qualities, the other two have never resurfaced. All that exists of Cathy's Valentine are two very short clips featured in a recorded commercial break from the day it aired, and a screenshot.
UPDATE 13 July '15: User ThingsIFoundInMyBasement has uploaded the two missing "Cathy" specials---"Cathy's Last Resort" and "Cathy's Valentine"---to YouTube.
Images & screenshots
"Valentine" ad featured in the TV Guide magazine (February 4-10, 1989).
Screenshot #1 from Valentine.
Screenshot #2 from Valentine.
Screenshot #3 from Valentine.
Last Resort press photo.
