Trev Fleming will create 300 improvised characters over the course of a 300-minute-long performance at 81 Renshaw Street in Liverpool on July 30.
Using one-word suggestions from the audience to inspire his scenes, he will be backed up by members of Liverpool improvised theatre company Impropriety.
All profits generated by the performance will be donated to Cancer Research.
The show begins at 3PM and is made up of six episodes of 50 minutes each, with a ten-minute break for the performers and audience.