Doll and Finn are two dolphins (a sister and a brother, respectively) who swim around together.
After Finn is captured by Octavia the octopus queen, Doll contacts harbor rescue officers Pablo and Tyrone. Doll and the officers run into Pilot Austin, who takes them the seafloor. The four are soon joined by mermaids Uniqua and Tasha. The group is later locked inside Octavia's undersea dungeon, where they find Finn. Pilot Austin finds a lever to release the cage, but is caught by Octavia. Mermaid Tasha challenges Octavia to a race to achieve freedom. Tyrone rides Doll and wins the race.
The dolphins are bipedal. They are both blue and have white eyes with black pupils.
Doll and Finn have appeared in one Backyardigans performance: Sea Deep in Adventure.