Dexter is the manipulative giant whose plan is to rule the city of Quetzo. He is a notorious octopus who is the main antagonist to the protagonists.
Dexter has violet skin. He has blue spots on his head and two yellow eyes.
Several times, Flipper was able to save him. However, he changes his mind to defeat him. Dexter lives in a grotto, assisted by three sharks (who are his henchmen). Although he praises himself for 'excellence', Dexter is very devious. He is known to deceive several episodic characters. One example is teaching a whale to see who is the strongest. It is revealed that Dexter actually tricked him into pushing the iceberg into the island.
- Dexter is very similar to Dave from the film "The Penguins of Madagascar". Both, he and Dave are octopuses and depicted as main antagonists.
- Dexter has a sister named "Dolores".