Billy is sitting in the waiting room of a law office. His mom comes out to grab him and tell him they’re going to see his grandpa. Irving Zisman is sitting in the waiting room of a hospital, checking out a magazine and looking at the sexual images. A nurse comes in to tell Irving that his wife has died. After a brief moment of silence, Irving starts laughing, overjoyed that his wife is dead. Irving leaves the hospital to get himself off, but unfortunately for him, the massage parlor and strip club are closed. Desperate, he sticks his penis in the slot of a vending machine. That’s when he gets himself stuck and starts asking onlookers for help.
Irving attends his wife Ellie’s funeral with a group of strangers. As he starts giving a speech, Billy and his mom Kimmie barge in and Kimmie pulls Irving out to talk to him. She says she’s going back to jail for violating her parole, and she asks Irving to make sure Billy stays with his father. Irving reluctantly agrees and they re-enter the church. Kimmie starts to steal a pearl necklace from Ellie’s casket, but Irving goes to stop her. Their struggle ends up pushing Irving into the casket, spilling Ellie’s corpse onto the floor.
Irving takes Billy to meet with a counselor while they contact Billy’s dad. Chuck turns out to be a deadbeat who refuses to take Billy in as he cannot afford to. When his girlfriend comes in to remind him that he can get child support for Billy, he instructs Irving to take Billy down to Raleigh, North Carolina to drop him off with him by Sunday. Irving starts selling Ellie’s belongings, and tries to sell her bed to a potential customer. Later, Irving calls a couple of unwitting guys to come help take the bed out, though he really asks them to help him and Billy carry Ellie’s body to the trunk of his car, since he felt that she needs to be taken south to be buried properly.
Irving and Billy hit the road, and Billy says he’s hungry, so Irving pulls over to a nearby market where a woman is selling food. He tries to hit on her while Billy goes on a ride outside the shop. He tells Irving that it’s not working, forcing Irving to test it out. He ends up getting shot through the window as the ride springs off its base. Frustrated, Irving tries to ship Billy off to North Carolina in a box. He takes him to the post office, but because Billy keeps moving and speaking, the two women in the place open it and are shocked to find him in there. Before he can get in anymore trouble, he says he’ll just take Billy back on the road. Irving leaves Billy in the car as he goes to a rec center to play Bingo. Meanwhile, Billy leaves the car to walk around and stop an older gentlemen to get him to tie his shoe.
The two stop in a supermarket when Billy gets hungry again, Irving takes food from the store and makes himself and Billy sandwiches, which is seen by the employees. A woman comes out to chastise Irving for eating without paying. The two pull into a motel for the day. They pull Ellie’s corpse out of the trunk since Irving thinks it would be disrespectful to leave it in the car. Irving then asks a man if he knows where a strip club is. The man points him out to one and he leaves Billy in the room. Irving goes to a club featuring male performers, and tells one of the dancers that he plans on waiting until the women are so aroused by the dancers for him to swoop in and make his move. When the men start to dance, Irving jumps on the dance floor and pulls down his pants. At the same time, Billy leaves the motel room to find Irving. He goes to another strip club and then to an adult book store. Irving eventually comes back home before they have to hit the road again.
As they near North Carolina, Irving tries to use Billy to find a woman to hook up with, but they all turn him down. They drive to a diner where Irving drives into a large penguin statue, arguing with one of the employees about fixing it. In the diner, Billy asks why he has to stay with his dad when he doesn’t like him very much. Irving insists that he has to go with him. They leave and later play some basketball while Billy asks Irving if he can take him fishing. Billy gets hungry yet again and Irving takes him to a church where a wedding reception is taking place. During a group photo, Irving swipes a glass of champagne, causing the whole tower of glasses to collapse, and he ends up falling on top of the table and into the wedding cake, crashing onto the floor.
Irving drives Billy to a bar where they are meeting Chuck. Chuck is talking to a member of a biker organization called Guardians of Children, who help abused kids. Chuck explains that Billy will allow for him to get child support just as Irving and Billy walk in the door. Irving asks him to make sure that Billy is taken care of, though he rudely responds to Irving that he’ll get the job done. Irving bids Billy farewell. As Irving leaves tearfully, one GOC member comes out to assure him that they’ll keep their eyes on Billy. Irving drives away, but quickly starts to miss Billy. He turns the car around and drives back to the bar to get Billy back, just as Chuck is showing off his bad parenting by denying Billy any food. Irving calls Billy to him, but Chuck prepares to fight him. The GOC members pull the two away from each other and allow Irving to leave with Billy while they hold Chuck off and warn him there will be trouble if he acts threateningly.
To celebrate, Irving and Billy crash a beauty pageant after spotting a flyer for it on their road trip. Billy gets dressed up as a girl and charms most of the judges, even though one reigning child champion and her mother note the unusual event of a girl being there with a grandpa. Billy dresses up as a sailor girl to put on a show while. It appears cute until he rips off the outfit to reveal him wearing women’s underwear and then put on a risque dance to “Cherry Pie”, then for Irving to throw money at him. Everyone, including the judges, are completely speechless. His wig falls off and the two run out. Irving drives up to a bridge where he and Billy finally get rid of Ellie’s body by throwing it into the river. The two then proceed to fish, fulfilling Billy’s desires.