From the Super Mario Wiki
Captain Clump is a pirate who inhabits Pirate World, the waters of which, he sails on his ship; Captain 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, hired Mario, Luigi, Toad and Princess Toadstool as his shipmates to help him sail through Pirate Waters. Sometime after hiring Mario, Luigi and Toad though, Captain Clump began 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 Captain Clump revealed that Blackbeard Koopa was sailing Pirate Waters to Mario, Luigi and Toad, his ship was enveloped by a thick, red haze. It was only after Mario cut a hole through this haze that Captain Clump noticed the ship of Blackbeard Koopa was nearby. Seeing that Captain Clump's ship was nearby and Captain Clump, Mario, Luigi, Toad and Princess Toadstool were on it, Blackbeard Koopa ordered them to surrender. Disobeying Blackbeard Koopa's order, Captain Clump raised his sword in defiance and told Blackbeard Koopa he would never surrender to him. It was this defiance that caused Blackbeard Koopa to attack Captain Clump's ship with Bob-ombs and later invade it with his Koopa Pirate Pack.
Despite fighting quite well against the Koopa Pirate Pack, Captain Clump, as well as Mario, Luigi and Toad, were defeated and tied to the mast of Captain Clump's ship, while Princess Toadstool was kidnapped by Blackbeard Koopa. As his ship was left to sail, directionless, Captain Clump struggled 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.
It was only when Luigi was splashed in the face by some water that Captain Clump realized that his ship was sinking, Blackbeard Koopa having drilled holes in the haul of it. It was only when Mario made an unsuccessful attempt to jump free of the ropes that Luigi realized that by squirming, he, Mario, Toad and Captain Clump could move upwards on the mast they were 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 awakened 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 through a Starman to Mario, who used the powers it endowed him with to free himself, Captain Clump, Toad and Luigi free their restraints and to defeat the Trouters who had begun to circle Captain Clump's sinking ship. Now freed from their bonds, Captain Clump, Luigi and Toad managed to climb into the unsunken crow's nest of Captain Clump's completely submerged ship. Using Captain 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, informed Mario that they were approaching Pirate's Port in their makeshift, crow's nest boat. Soon after reaching Pirate's Port, Captain Clump and Toad managed to gain access Blackbeard Koopa's fortress after Mario and Luigi, disguised as pirates, gained permission to enter it from it's Koopa Troopa guards.
Once inside the fortress, Captain Clump and Toad were instructed to get near Princess Toadstool, who was being held in a cage, while they distracted Blackbeard Koopa and his Koopa Pirate Pack. As Toad freed Princess Toadstool, Captain Clump kept watch and when Blackbeard Koopa and his Koopa Pirate Pack discovered that Mario and Luigi were in their fortress, it was Captain Clump who yelled for them to run.
After being chased to Blackbeard Koopa's ship, Captain Clump aided 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 helped 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.