Doug discovers that though being Harry's best friend in Miss Mackle's second grade class isn't always easy, as Harry likes to do horrible things, it is often a lot of fun.
Mom has agreed: Froggy can have a pet. Off to the pet store they go. Mom would prefer a bunny or some mice, but Froggy and his little sister, Pollywogilina, have their hearts set on a doggy. And when Froggy sees the little dog with big brown eyes, he begs to take her home.
When Joe the giraffe and his friend Sparky, a turtle, get curious about a big yellow bus that comes to their cageless zoo, they find themselves accidentally taking a trip to school, where they discover a lot to do and learn.
Froggy hoped for a brother to play with so he is disappointed with his new baby sister, Pollywogilina, but only until she is old enough to start learning from her big brother.
As Valentine's Day approaches, Froggy thinks that he is falling in love with the new girl in class, but his feelings change when she gives him their first kiss.
Follows the school activities of second-graders, Harry and Doug, as they participate in a secret mission to celebrate "Charlotte's Web," learn how to make green slime, and put on a skit warning about the dangers of smoking.
Froggy isn't looking forward to his check-up because he might get a shot but when it's over and he's pronounced a very healthy frog, Dr. Mugwort is the one who dreads Froggy's next visit.