Rex and her best friend Pinky, each the proud possessor of twenty-seven stuffed animals or dinosaurs, find their visit to the museum and its gift shop complicated by Pinky's little sister Amanda.
Pinky, Rex, and Amanda plot revenge on the bad-tempered old woman who lives across the street, until Pinky realizes that she is lonely and needs new friends.
Excited about holding onto his position as the best speller in the second grade, Pinky has an embarrassing accident but is cheered up by his best friend Rex.
Determined to be a good big sister, Rex starts spending all her time with the baby her family has adopted, making her neighbor Pinky fear that he has lost her friendship.
Rex and her best friend Pinky are upset to learn that their friend and neighbor Mrs. Morgan is moving, and it looks like a family with an obnoxious boy named Ollie is set to move in.
When Rex accompanies Pinky and his relatives on their traditional trip to pick and carve pumpkins, she feels left out because of the jealous behavior of Pinky's cousin Abby.
