From the Super Mario Wiki
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, ventured to Dealin' Delbert's cow lot. Once Mario and Luigi arrived at Dealin' Delbert's cow lot, they were continually hassled by Dealin' Delbert to trade their cow for one of his cows, all of whom looked either old, sick or were generally just in bad shape.
After Mario and Luigi refused to sell their cow, wanting only to sell it, Dealin' Delbert decided to make them a special deal, giving them something special in exchange for their cow; it was eventually revealed that Dealin' Delbert had, in actuality, traded Mario and Luigi three small garbanzo beans for their cow. These Garbanzo beans were later revealed to be capable of growing into a gigantic beanstalk, though whether Dealin' Delbert knew these Garbanzo beans could do this is unknown.
It is also revealed in this episode that Princess Peach is allergic to these "garbanzo beans"