The Reverse Peephole [SEP] series
The Reverse Peephole
"The Reverse Peephole" is the 12th episode of the ninth season of the television comedy series (the 168th overall), "Seinfeld". It was written by Spike Feresten and directed by Andy Ackerman. 
Plot.
Elaine, Jerry and George decide to buy a massage chair for their friend Joe Mayo but when Elaine suggests Bloomingdale's, George says he will take responsibility to find a cheaper one. Kramer and Newman reverse the peepholes on their apartment doors to spot any ambushes inside their rooms
cast wearing different costumes and hairstyles throughout the series. That includes "The Puffy Shirt", "The Barber", "The Wig Master", "The Subway", and "The Reverse Peephole".
Plot Part 2.
Jerry continues to reflect the nine years that have passed until Kramer (in character) comes up to get Jerry. He then breaks the fourth wall by noticing the camera and smiling. 
More clips are seen and finally the closing minutes feature a series of bloopers, behind the scenes