From the Super Mario Wiki
Captain Clump is a pirate who inhabits Pirate World, the waters of which, he sails on his ship; Clump seems to a mixture of several pirate stereotypes, having an eyepatch, a hook in place of a hand, a peg leg which is quite large in size, and a parrot named Patches.
In The Super Mario Bros. Super Show! episode "Pirates of Koopa", Captain Clump, needing a new crew for his ship, hires Mario, Luigi, Toad and Princess Toadstool as his shipmates to help him sail through Pirate Waters. Sometime after hiring Mario, Luigi and Toad though, Clump begins to become increasingly irritated by them, saying the only reason he hired them to join his crew was because his original one had abandoned him, not wanting to sail with Blackbeard Koopa and his Koopa Pirate Pack on the prowl.
Soon after Clump reveals that Blackbeard Koopa is sailing Pirate Waters to Mario, Luigi and Toad, his ship is enveloped by a thick, red haze. After Mario cuts a hole through this haze, Captain Clump notices the ship of Blackbeard Koopa is nearby. Seeing that Clump's ship is nearby and Captain Clump, Mario, Luigi, Toad and Princess Toadstool are on it, Blackbeard Koopa orders them to surrender. Disobeying Blackbeard Koopa's order, Clump raises his sword in defiance and tells Blackbeard Koopa he will never surrender to him. This defiance causes Blackbeard Koopa to attack Captain Clump's ship with Bob-Ombs and later invades it with his Koopa Pirate Pack.
Despite fighting quite well against the Koopa Pirate Pack, Captain Clump, as well as Mario, Luigi and Toad, are defeated and tied to the mast of Captain Clump's ship, while Princess Toadstool is kidnapped by Blackbeard Koopa. As his ship is left to sail, directionless, Clump struggles in vain to escape the ropes tieing him, Mario, Luigi and Toad to his ship's mast, becoming annoyed by Luigi's optimistic singing in the process.
When Luigi is splashed in the face by some water, Captain Clump realizes that his ship is sinking, Blackbeard Koopa having drilled holes in the haul of it. Mario makes an unsuccessful attempt to jump free of the ropes, and Luigi realizes that by squirming, he, Mario, Toad and Captain Clump can move upwards on the mast they are tied to. After several minutes of wriggling up the mast, Captain Clump, along with Toad, Mario and Luigi, hit their heads on the crow's nest atop the ship's mast.
Luckily, Captain Clump, Mario, Luigi and Toad hitting their heads on the crow's nest awakens Patches, who had been flung into it during the battle against Blackbeard Koopa and his Koopa Pirate Pack and knocked unconscious. After hitting his head, Patches throws a Starman to Mario, who uses the powers it gives him with to free himself, Captain Clump, Toad and Luigi free their restraints (though the three accidently fell into the water, except Mario) and to defeat the Trouters who had begun to circle Captain Clump's sinking ship. Now freed from their bonds, but completely wet from falling in the water, Clump, Luigi and Toad manage to climb into the unsunken crow's nest of Captain Clump's completely submerged ship. Using Clump's sword, Mario manages to cut the crow's nest free from the ship and use it as a boat to sail to Pirate's Port.
Sometime later, Captain Clump, using his telescope and acting as a lookout for Mario, informs Mario that they are approaching Pirate's Port in their makeshift, crow's nest boat. Soon after reaching Pirate's Port, Clump and Toad manage to gain access Blackbeard Koopa's fortress after Mario and Luigi, disguised as pirates, gain permission to enter it from it's Koopa Troopa guards.
Once inside the fortress, Clump and Toad are instructed to get near Princess Toadstool, who is being held in a cage, while they distract Blackbeard Koopa and his Koopa Pirate Pack. As Toad frees Princess Toadstool, Clump keeps watch and when Blackbeard Koopa and his Koopa Pirate Pack discover that Mario and Luigi are in their fortress, Captain Clump yells for them to run.
After being chased to Blackbeard Koopa's ship, Clump aids Mario, Luigi, Toad and Princess Toadstool in battling the Koopa Pirate Pack on it; after being narrowly saved by Patches from a Bob-Omb, Captain Clump helps Mario, Luigi, Princess Toadstool and Toad in tieing Blackbeard Koopa to the rigging of his ship, using that as a slingshot to finally vanquish Blackbeard Koopa from Pirate World.