When Marsha learns she has missed her date with her summer camp crush Greg Hastings, Billy and Zeke attempt to cheer her up by fixing her up with a subterranean replacement.
Plot[]
Billy returns to the house from collecting a mold specimen. As he and his friends sit to have lunch, Marsha tells the boys that she has a date with her summer camp crush Greg Hastings that very night. Billy and Zeke are confused by this claim as it would be impossible for Greg to come down and meet them in Subterranea-Tania. Marsha is in denial as she feels that their love for each other will not separate them. When Billy off handedly suggests her dating Anaximander or simply having Greg teleported there (which he admits would be difficult as his atoms would be split apart and put back together in unpredictable ways) Marsha cries and runs into her room.
Billy and Zeke feel bad for making Marsha cry and decide to set her up on a date using a mud man as a replacement. Placing him in a Greg Hastings costume, they bring him to Marsha, who does suspect a thing, and bring them out to a diner they have set up. As Billy acts as a waiter, Zeke is the chef and cooks "whatever [Greg] wants". Billy and Zeke cause some shenanigans in the kitchen as they struggle to keep Marsha from learning the truth. Eventually, everything seems to work out fine until a fake moon they have acquired turns out to be a pteranodon egg that hatches and reveals the mud man. The pteranodon makes off with Zek and Marsha and Billy resolves to rescue them.
After getting dragged to the pteranodon's lair, he spots it about to devour Zeke and Marsha and runs in front of it where he gives an impassioned speech about how one cannot manufacture love and how he just wanted to make Marsha happy. He allows himself to be eaten by the pteranodon in place of his friends, but the mold that he was hanging onto all day causes the pteranodon to shrink down. The friends head back home with the pteranodon now a pet for Marsha. She thanks them for trying to make her happy, but the gang discover too late that the effects of the mold are temporary as the pteranodon returns to normal giant size.
