Dad-Not-Dad is the tenth episode of Season 4 and the 46th overall episode.
Jimmy spends a day with a woman from his past and attempts to fit in with her friends; Gretchen tries to impress Boone's ex-wife; Lindsay reconnects with a former father figure; Edgar buys a car that he cannot afford.
Lindsay and Becca go on a search for their former father figure, Lou Diamond Phillips, who used to be their mom's paramour but now spends his days ineffectually managing a lemon orchard.
He tells them that Faye kicked him out of her life and made him promise to never come around her kids, but by episode's end he and Faye are hooking up again and he gives Lindsay and Becca decent advice.
Gretchen tries to win over Boone's ex-wife Whitney (Anne Dudek) so she can spend time around Boone's daughter Olivia. Whitney breaks down over her life no longer being "fun" and gets drunk with Gretchen, who blacks out. She comes to in the middle of sex with Whitney at Lindsay's apartment.
Jimmy tries to fit in among his old classmate Katherine's smart, talented and successful new friends, but only reveals himself to be a "rube" who is cast aside by them. This adds to Jimmy's generally bad and shunned day, as his good advice for Edgar to avoid buying a car he can't afford (under the malign influence of Max) is angrily brushed aside by Edgar.
Gretchen tells Boone she doesn't need to have any contact with Jimmy anymore, but soon sends a text to Jimmy saying "we need to talk."