Make Room for Lisa.When Homer uses Lisa's room as a cellular phone transmitter to pay off damages he did to the Bill of Rights at a Smithsonian exhibit, Lisa is forced to move into Bart's room. Lisa becomes furious with her father for having to share a room with her brother. She fears that she and Homer will never be close because of their clashing personalities and begins to develop stress-related stomach aches. To relieve these aches, Homer and Lisa visit a New Age store where the owner convinces them to go on a spiritual journey by lying in a sensory deprivation tank for a prolonged amount of time. On her journey, Lisa discovers that beneath Homer's bumbling outside, he really does care about her. Reconciled, the two of them watch a demolition derby together, something they equally enjoy. Meanwhile, Marge uses Maggie's monitor to listen in on other people's phone calls; however, when Milhouse and Bart play a prank on her, Marge knocks Milhouse out, thinking he was a burglar.