Mervin the Magician
From the Super Mario Wiki
“ Dust off the crown, and call out the town! Cramalot has a new king!”
Mervin the Magician is a powerful magician and inhabitant and seemingly the protector of the kingdom of Cramalot.
In The Super Mario Bros. Super Show! episode "King Mario of Cramalot", Mario, Luigi, Princess Toadstool and Toad travel to Cramalot in search of Mervin, who they believed could free Princess Toadstool's kingdom of King Koopa's rule.
On the road to Cramalot, Mario, Luigi, Toad and Princess Toadstool are attacked by a gang of Beezo; it is only through the intervention of Mervin that Mario, Luigi, Toad and Princess Toadstool are saved from the Beezo, who Mervin seemingly vaporizes with his wand. After defeating the Beezo, Mervin, along with Mario, Luigi, Toad and Princess Toadstool travel to Mervin's cave, where Mervin reveals that King Koopa has taken over Cramalot.
After telling Mario, Luigi, Toad and Princess Toadstool of King Koopa's conquest of Cramalot, Mervin reveals that, whoever can pull the Golden Plunger from the Sacred Sink of Cramalot will be able to defeat King Koopa.
After revealing this, Mervin takes Mario, Luigi, Toad and Princess Toadstool to the town square of Cramalot, where he instructs Mario to remove the Golden Plunger from the Sacred Sink of Cramalot, which Mario succeeds in doing. Unfortunately, as Mario, Luigi, Toad, Princess Toadstool and Mervin celebrate Mario's claiming of the Golden Plunger, they are captured by King Koopa and his Koopa Troopas and Koopa Paratroopas.
Despite using his Golden Plunger to escape a net dropped on him by King Koopa's Koopa Paratroopa minions, Mario, as well as Mervin, Luigi, Toad and Princess Toadstool are captured by King Koopa, who also claims the Golden Plunger as his own.
It seems Mervin had somehow evaded capture by King Koopa, as he later appeared in the dungeon of Cramalot Castle and, using his magic wand, teleported Mario, Luigi, Toad and Princess Toadstool from their rapidly flooding cell. After leaving Cramalot Castle, Mervin brought Mario, Luigi, Toad and Princess Toadstool to the Forest of Perpetual Night and Terrible Dangers; in this forest, Mario discovered the legendary Excalibur, which he planned to use against King Koopa.
Later, Mervin aided Mario, Luigi, Toad and Princess Toadstool in their siege of Cramalot Castle, where he defeated several of King Koopa's Koopa Troopa henchmen.
In the end, King Koopa is defeated by Mario, who is crowned the new king of Cramalot by Mervin; unfortunately, it turned out that the king of Cramalot had to be physically fit, meaning Mario had to go on a diet and eat healthy food to be Cramalot's king. Horrified by this prospect, Mario gave his crown to Mervin, who he decided to be Cramalot's new king.