NBC announced on Monday that the actor's storyline, which is due to wrap up on April 28, will span 50 minutes rather than its usual 30 during the Thursday night primetime lineup.
The episode will occupy its usual 9pm timeslot and run until 9.50pm. Parks and Recreation will follow with its own supersized episode from 9.50pm to 10.30pm.
Several stars are reportedly in the running to replace Carell, including Catherine Tate, James Spader and Will Arnett, all of whom will appear on the show's season finale.
Will Ferrell will appear in a four-episode arc as a potential candidate for the open office manager position, but is not expected to join the series full time.