R Mart is a convenience store in Stoolbend.
In "Frapp Attack!", Donna takes Hollywood producer Willy Nilly there as he shadows her to convince her to let Cleveland go to Hollywood on a record deal. As she tries to explain what things are like for normal people she begins by showing him about pumping her own gas which he confuses for making a baby car. Later when Cleveland gets fed up with Willy trying to take his life, he shows him exactly what happens in it including constantly stopping at the R Mart in order to buy eggs for Donna.