Henry and his big dog Mudge celebrate Henry's birthday with a pi?nata, a lively birthday party, and a cake shaped like a fish tank, making May first the best day ever.
Henry and his dog Mudge are invited to a sleepover in Patrick's attic, where they watch monster movies, eat pizza, and enjoy a contest to determine whose dog is the best popcorn catcher.
While Henry's parents are at a Sweetheart Dance on Valentine's Day, he and his dog Mudge have a wonderful time staying at Mrs. Hopper's house, where they enjoy tea and music and dressing up in various costumes.
At first Henry's very neat cousin does not like the cookies from under his bed or Mudge's slobbery kisses, but when they all play frisbee, she begins to enjoy her visit.