5x14 - Little House on the Prairie

In this episode starring twins Lindsey and Sidney Greenbush, Charles takes a job on a telephone crew that is working in southern Minnesota, which requires him to be away from home for several weeks. Carrie, heartsick for her Pa and craving attention, only manages to get into everybody else's way, so the lonesome tyke creates an imaginary friend, Alyssa, to ease the pain.