University of Barcelona researchers noted that dogs in classic Disney films frequently seem to exhibit REM behavior disorder (RBD). Below is the full abstract for their scientific paper, published in a 2007 issue of the journal Sleep Medicine:
During a viewing of Disney’s animated film Cinderella (1950), one author (AI) noticed a dog having nightmares with dream-enactment that strongly resembled RBD. This prompted a study in which all Disney classic full-length animated films and shorts were analyzed for other examples of RBD. Three additional dogs were found with presumed RBD in the classic films Lady and the Tramp (1955) and The Fox and the Hound (1981), and in the short Pluto’s Judgment Day (1935). These dogs were elderly males who would pant, whine, snuffle, howl, laugh, paddle, kick, and propel themselves while dreaming that they were chasing someone or running away. In Lady and the Tramp the dog was also losing both his sense of smell and his memory, two associated features of human RBD. These four films were released before RBD was first formally described in humans and dogs. In addition, systematic viewing of the Disney films identified a broad range of sleep disorders, including nightmares, sleepwalking, sleep related seizures, disruptive snoring, excessive daytime sleepiness, insomnia and circadian rhythm sleep disorder. These sleep disorders were inserted as comic elements. The inclusion of a broad range of accurately depicted sleep disorders in these films indicates that the Disney screenwriters were astute observers of sleep and its disorders.
“REM sleep behavior disorder and other sleep disturbances in Disney animated films” (via NCBI ROFL)