After he leaves Lucynell at the diner whom does Mr. Shiftlet pick up

He picks up a boy wearing overalls who is hitchhiking with a suitcase.

Soon, he picks up a boy wearing overalls who is hitchhiking with a suitcase. Tom Shiftlet begins to talk to the boy, who is unresponsive at first. He talks about his mother, whom he praises as "the best old mother in the world," and muses that the worst day of his life was when he left her. This is clearly making the boy uncomfortable. As Tom Shiftlet begins to tear up from talking about his angelic mother, the hitchhiking boy tells him, "You go to the devil! My old woman is a flea bag and yours is a stinking pole cat!" and throws himself from the passenger door. A storm cloud descends and it starts to rain as Tom Shiftlet continues to drive toward Mobile.