The puzzle is sometimes told with a fox, a chicken, and a bag of seed, but the principle is the same. Ralsei mentioned this in earlier versions of the comic, but I cut that to get to the point.
Yes, there's a reason Susie is watching a Wile E. Coyote-esque cartoon, but it's not because foxes and coyotes are both canines. It's a story for the future. I'm also not sure what the existence of that cartoon implies. Like, is there a reality below the Dark World of beings who exist to entertain the Darkners?
You might be wondering why Spamton is wearing the dinosaur pajamas when the blue suit-like pajamas are more his style. I just thought putting him in the dino jammies was funnier. As for the story reason for why he'd be wearing them, pick whatever reason you like best:
A) Spamton is afraid Susie will beat him up if he doesn't seem to appreciate her gift.
B) Ralsei hung both pajama sets on the towel rack, but Susie snuck the blue pajamas out.
C) Susie offered to hang the pajamas on the towel rack, Ralsei foolishly trusted her, and she "forgot" the blue pajamas.
I personally like C best, but whatever floats your boat.