From the Super Mario Wiki, the Mario encyclopedia
Dealin' Delbert is the owner of a cow lot and somewhat of a swindler and con man; Dealin' Delbert is never seen without a cigar in his hand, he also wears a cowboy outfit and has an abnormally long nose.
In The Super Mario Bros. Super Show! episode "Mario and the Beanstalk," Mario and Luigi, needing to sell Princess Toadstool's pet cow for one hundred Gold Coins, venture to Dealin' Delbert's cow lot. Once Mario and Luigi arrive at Dealin' Delbert's cow lot, they are continually hassled by Dealin' Delbert to trade their cow for one of his cows, all of whom look either old, sick or were generally just in bad shape.
After Mario and Luigi refuse to trade their cow, wanting only to sell it, Dealin' Delbert decides to make them a special deal, giving them something special in exchange for their cow; it is eventually revealed that Dealin' Delbert had, in actuality, traded Mario and Luigi three small garbanzo beans for their cow. These Garbanzo beans are later revealed to be capable of growing into a gigantic beanstalk, though whether Dealin' Delbert knows these Garbanzo beans can do this is unknown. It is also revealed in this episode that Princess Toadstool is allergic to these "garbanzo beans".