When Helen is cast as Halley's Comet in the school play, Martha the talking dog helps her to overcome stage fright, and later Martha struggles to play the Cheshire Cat.
Amelia Bedelia's request for a sibling takes her parents by surprise, but she is soon distracted by the possibility of finding the perfect puppy, instead.
A well-bred Lhasa Apso named Gulliver is forced to leave his master and finds a new one named Carlos, the doorman of a Manhattan apartment building, who takes the dog to his place in Queens, where Gully meets low-life mutts and boisterous humans.
The gang want to check out the new store at the mall, Dr. Yuckenstein's Make-a-Monster; but when a mega-sized monster comes to life and scares away all the customers, it's a monster of a mystery that only Scooby-Doo can solve.