Michael K . Frith drawings During his time with the Muppets , Michael K . Frith provided a vast number of design sketches which shaped the look of characters , sets , and props in Muppet productions , as well as illustrating licensed merchandise and books . Like Jim Henson , Frith ' s sketches were often done on notepads , ruled notebook paper , napkins , and other materials , in rough black form , as well as in more detailed colored suggestions and final presentation materials . In September of 2007 , HIT Entertainment and The Jim Henson Company released a set of sketch reprints from Frith ' s work on " Fraggle Rock " in . Early Character Designs . Frith first worked with the Muppets as an editor and illustrator of the " Sesame Street " storybooks line while working at Random House . His earliest direct contributions to Henson ' s work included designs for " Muppet Musicians of Bremen " . His first full - time job for Henson , in 1975 , was designing a series of new Muppets to appear on " Saturday Night Live " . Frith ' s designs , as already evident even in abstract characters , often featured a more realistic approach towards characters , caricatures creating an illusion of visceral reality as opposed to more purely cartoon figures . The Muppet Show . By the time of " The Muppet Show " , Frith had become a key designer and full - time art director for merchandise as well as characters . Though many pre - existing characters were used on " The Muppet Show " , and though Jim Henson still contributed designs and ideas , many of the new regulars and a large number of the special one - shot characters were designed by Frith . The sketches were sent to both New York and London workshops , and helped to define a consistent look for the new characters . Though more realistic representations still continued , the designs for this production , especially the color sketches , were brighter and more cartoony , blending anthropomorphic complexity with the whimsical aesthetic and principles previously pioneered by Henson and Don Sahlin , particularly evident in the eyes . Fraggle Rock . Frith ' s involvement in " Fraggle Rock " began early on , concurrent with the general concept development for the series and preceding the actual script - writing , as discussed in the DVD documentary feature , and accompanied by the original artwork . Though many of the specifics changed or developed prior to the actual show , the general look and feel of the characters was already set in the illustrations , which were collected into a concept booklet and used for the show pitch . Unlike " The Muppet Show " , where sets and prop decorations were almost exclusively the domain of the London art directors working outside of the Workshop , Frith ' s designs for the series included set and prop suggestions as well . Locations such as the rock itself or the Gorgs ' castle were designed by Frith , then translated into another set of sketches by set designer William Beeton highlighting the practical dimensions and finally translated into the actual project . Muppet Babies . Frith ' s designs guided the basic look of the " Muppet Babies " in puppet form , and additional designs were created especially for the animated version .