"The Substitute" is the seventh episode of the second season of the American television series Glee. It was the 29th episode of the entire series. The episode was directed by Ryan Murphy and written by Ian Brennan. It was first broadcast on FOX on November 16, 2010. The episode was watched by 11.70 million people in the United States. It was the top scripted show among adults aged 18–49 for the week it was broadcast. The episode guest stars Gwyneth Paltrow as Holly Holliday. She is a substitute teacher who does Will Schuester (Matthew Morrison) job as glee club director while he is sick. Cheerleading coach Sue Sylvester (Jane Lynch) becomes principal of William McKingley High School, and glee club members Mercedes Jones (Amber Riley) and Kurt Hummel (Chris Colfer) start to feel stress in their growing friendship.
The episode includes cover versions of six songs. These songs got mixed reviews from music and television journalists. The cover version of Cee Lo Green's "Forget You" and mash-up of "Singin' in the Rain" with Rihanna's "Umbrella" was given good reviews. Both covers' charted on the Billboard Hot 100. Paltrow's guest appearance was given positive reviews. The sub-plots of the episode did not get good reviews. Aly Semigran of MTV, Robert Canning of IGN and Entertainment Weekly's Tim Stack all thought that "The Substitute" is the best episode of the season. Time's James Poniewozik said that the episode was an "okay" episode. Todd VanDerWerff of The A.V. Club said it was better than the previous two episodes. The National Alliance on Mental Illness gave positive reviews for the episode's definition of bipolar disorder. Paltrow won the 2011 Primetime Emmy Award for "Outstanding Guest Actress in a Comedy Series" for her acting.