From the Super Mario Wiki
(Redirected from Dino of Mystery!)
When the player decides to stop here, he or she meets Mr. E. He explains to the player that he has heard about a monster lurking in these waters, when all of a sudden, a Dorrie comes out and frightens him away. Dorrie's quest, Dino of Mystery!, involves playing as Yoshi. All Yoshi must do is accept Dorrie's friend request to get the Soil Sonar Gaddget.