Arby's is a fast food restaurant in the U.S.
When the members of Springfield Elementary' Model U.N. Club stranded on an island in the middle of nowhere. There was no food on the island, so Terri or Sherri said that they are so hungry they could "eat at Arby's". It then caused other children to gasp.
When Santa's Little Helper became a new mascot of Duff Beer, he started appear in various beer commercials. In one, he was showed partying with some young women. During watching the ad, Lisa asked why a dog would have human girlfriends. Marge told her that people do crazy things in ads, "like eat at Arby's".
When Kirk Vanhouten separated from his wife Luann and was living in an apartment, he proposed disposing of a dead opossum by throwing it over the fence into Arby's parking lot.
When Homer was trying to eat the blob, he said that if he could "keep down Arby's", then he could "keep down" the blob.