Kate was out sick for a month with mono, and when she came back to school, Jessie had supplanted her as the funny girl at the lunch table. Supplant means to take the place of.
Being supplanted is something that often happens to ideas or ways of thinking. Encouraging children's freedom has supplanted old ideas about children being better seen than heard. After a shocking upset at Wimbledon, a new tennis player has supplanted the reigning champion.