Quest for a punchline is a four map series that takes place in a short window of time right at the end of portal 2. It follows the adventures of an early P-body prototype dated back from the late brain mapping experiments and who's subsequent decommission happened shortly after the success with GlaDOS.

You are woken up by GlaDOS many years later for a special task that requires your attention. Mainly because you are the only one in the area.