Doug's Sister Act is the second part of the eleventh episode of the fourth season of Nickelodeon's Doug.
Theda invites Judy's new boyfriend over for dinner, but Judy is embarrassed of her boring family, especially Doug. So she decides to "spruce" things up around the house.
Doug's Journal Entry: Dear Journal. It seems that every time I go to the Moody School, there's trouble. Today, we were just going to pick up Judy, but we haven't counted on Judy's latest boyfriend.
Theda is driving at the Moody School along with Doug to pick up Judy, who tries to get into the car and tell Theda to drive. But her boyfriend Kyle catches her and introduces himself to Theda, who invites him over for dinner tonight. Judy is embarrassed of this fact and chides Theda for it. Doug then nonchalantly asks Theda what she is cooking for dinner.
During the afternoon, Judy is having a hostile argument with Theda at the Funnie house. Judy enter Doug's room and persuades him to back her up, but Doug says that he wants no part of it. Judy reminds him of what happened when her last boyfriend came to have dinner with the family (in which he fainted from boredom in a bowl full of mashed potatoes after Phil offers him gravy, which has broken the long silence) and says that she dislikes the fact that the family is dull. When Doug sarcastically says, "It's like you wants them to be characters in one of your stupid plays" when describing his parents, he inadvertently gives Judy an idea.
While Phil and Theda are cooking dinner, Judy gives her family a script to follow: Phil is playing a pirate poet and Theda is playing an anthropologist. Judy even has her friends to bring in the things for the imminent act and the family rehearse for it, reading their lines of the script Judy has offered him. Doug imagines what Judy would have him play.
Doug's imagination (two different scenarios): Kyle enters the Funnie house and Judy introduces him to Doug, who is portrayed as a wild boy; Kyle enters the Funnie house and Judy introduces him to Doug, who is portrayed as Smash Adams. He greets himself to Kyle and leaves via jet pack to save a president.
To his annoyance, however, Judy has him playing as the butler, saying that he is "way too dull to fit into the family" to get a part he wanted. So Doug, feeling angry and alienated, has a trick up his sleeve.
When Kyle arrives, Judy introduces him to Doug as Yancey the Butler right before introducing her parents to him. Doug leads Kyle to the supply closet and poses as a secret agent in front of him. He gives him a sponge and tries to tell him that he is really Special Agent Doug right before being interrupted by Judy, who walks into the closet, and Doug leaves, telling her that he is just getting the Hors d'oeuvres.
Later, at the living room table, which has a tray of lasagna on, Theda prepares dishes from Mogwai for Kyle in honor of his visit and Phil pretends to be in agony. Doug pretends to choke and falls to the floor. Judy takes him out of the room and tells Theda to start of her lecture. Kyle then reads a note in his glass of water that says "There's a Bomb in the Lasagna" and Doug, acting as the secret agent he wanted to be in the first place, dives into the lasagna and pretends to be dying. Kyle, along with the rest of the family, laughs at Doug's act. But Judy is little more than embarrassed and walks out of the house.
Knowing that he had pushed his sister too far, Doug walks outside to comfort her. He tells her that he was upset over the fact that she has told the rest of the family how dull they were and Judy apologizes to him, telling him that she only wanted Kyle to like her. Kyle comes around and tells her that he knew all along that it was a performance, even before Doug dove into the lasagna. Kyle mentions that there were a few problems in scene 3 (for instance, Theda made a reference to scene 4). Porkchop enters and licks the tomato sauce off of Doug's face.
Doug is later seen in his room watching his sister say goodbye to her boyfriend, who rides away on his motorcycle. Doug states voice-over that it is normal to be embarrassed by your family, stating seeing them everyday as the reason and to others, your family isn't really boring at all.