Pimpa receives a letter from Rabbit and rushes to the beach, where they play with his siblings. After they leave, she floats on a raft until the little fish Flip wakes her up—he needs a candle for Grandpa Fish’s birthday! Pimpa gives him one and joins the underwater party, where a fish band (Trombone, Trumpet, Drum, and Clarinet) and Boby the dogfish sing ‘Happy Birthday.’
Grandpa Fish shares his childhood dreams with Pimpa, especially his love for stargazing. She takes him to the surface on her raft to see the stars again. Meanwhile, Armando returns home but there isn't anybody, so Mirror Pimpa replaces Pimpa. Colombo arrives in Uncle Gastone’s rocket and whisks Pimpa and Grandpa Fish on a space adventure. Back home, Pimpa tells Armando everything before falling asleep, happy.