From the Super Mario Wiki
In The Super Mario Bros. Super Show! episode "Mario and Joliet", Romano and his fiancée, Joliet, were forced to go underground when their fathers began a feud against one another, which culminated in Romano's father and Joliet's father canceling Romano and Joliet's wedding. With her and Romano's father feuding, Joliet sent a message to Princess Toadstool, asking for her help in resolving this feud.
Eventually, in the tunnels beneath the Land of Romance, Romano and Joliet met Mario, Luigi, Toad and Princess Toadstool, who had fallen in the tunnels after an encounter with the Snifit, Albatoss and Bob-omb minions of Romano's father and Joliet's father. Greeting Mario, Luigi, Toad and Princess Toadstool, Joliet and Romano revealed that the feud between their fathers was caused by King Koopa. Hearing Romano and Joliet's story, Princess Toadstool decided that, as the official princess of the Mushroom Kingdom and, thus, the Land of Romance, she would order the feud between Romano's father and Joliet's father to be ended immediately, so Romano and Joliet could get married.
Princess Toadstool's plan actually does work, after some effort and Romano and Joliet's wedding proceeds as planned, with Mario, Luigi, Toad, Princess Toadstool and both Romano's father and Joliet's father, reluctantly, attending in a large church. Unfortunately, before the wedding can even begin, Toad informs everyone present that Joliet had been abducted as she was preparing for the wedding. Shocked at this revelation, Joliet's father accused Romano's father as his daughter's abductor and reinstated the feud between himself and Romano's father. As his father and Joliet's father had their Snifits attack one another, Romano lifts a trapdoor in the ground, which he, Mario, Luigi, Toad and Princess Toadstool leap down into, just as the church they are in begins to collapse due to the exploding projectiles launched by the nearby Snifits.
In the sewers beneath the Land of Romance, Romano states that he, Mario, Luigi, Toad and Princess Toadstool need to save Joliet and begins to wonder who had kidnapped Joliet; after some contemplating, Romano is told by Princess Toadstool, Mario, Luigi and Toad that King Koopa must have been the one who had taken Joliet. After telling Romano this, Mario, Luigi, Toad, Princess Toadstool, as well as Romano, went in search of Joliet.
After some traveling, Mario, Luigi, Toad, Princess Toadstool and Romano reached King Koopa's castle. At first, King Koopa's castle seemed unbreachable, though Mario eventually found a way to cross the castle's moat by using some nearby logs as stepping stones. Unfortunately, as he was using these logs to cross the moat to King Koopa's castle with Princess Toadstool, Toad and Luigi, Romano fell into the moat, attracting several nearby Trouters to him. Luckily, Romano manages to escape from the moat, narrowly avoiding a Trouter which was bounding towards. Shortly after rejoining Mario, Luigi, Toad and Princess Toadstool, Romano, as well as Mario, Luigi, Toad and Princess Toadstool, were captured by an Albatoss in a net.
Eventually, Romano, Mario, Luigi, Toad and Princess Toadstool are placed in a dungeon tower of King Koopa and his minion, Grunt. After a lot of difficulty, Mario, Luigi, Toad, Princess Toadstool, Romano and Joliet, after tricking Grunt into crashing through the floor, escaped their cell after Mario used Joliet's bouquet of Fire Flowers to become Super Mario. As they were escaping though, Mario, Luigi, Toad, Princess Toadstool, Romano and Joliet encountered King Koopa and his Koopa Pack, consisting of Koopa Troopa.
As Mario distracted these approaching Koopa Troopas, Romano, Joliet, Luigi, Toad and Princess Toadstool, using the door of their former cell and some of Grunt's weights, managed to make a vehicle. Using this newfound mode of transportation, Romano, Joliet, Toad, Luigi, Princess Toadstool, after picking-up Mario, managed to escape from King Koopa's castle.
After this adventure, Mario, Luigi, Toad, Princess Toadstool, Romano and Joliet returned to the ruined church of the Land of Romance, where Romano and Joliet were finally wedded.