ABOUT
Satan’s Lair is a comic strip created to string a series of animated .gifs together. All the animated .gifs portray someone or something falling through the floor usually in a comical or unexpected way.
Origin
The first time all the images were uploaded in one post was January 23rd, 2013 onto the Tumblr blog http://dave-stridlediddle.tumblr.com/post/41334468026
The main cannon involves a girl falling off a swing into a deep puddle. The puddle sends her into Satan’s lair, where he is reading a book.
Not long after that a man falls through a trap door into the lair on the other side of satan. Satan complains about getting a leak fixed and then a skateboarder gets stuck in the ceiling.
(As a comment) A horse climbs into a car which sinks into the ground and lands on Satan. Followed by Hawkeye and Thor (who gets stuck in the ceiling). Finally a person caked in mud faceplants a mudpuddle and falls into the lair.
It is at this point that the story spurs off into different directions and there are a few different narratives. Including one with an ice skater: http://shane-ss.tumblr.com/post/43514084597/rangerkimmy-theskadudeguy
and one with an anime character caled Beryl: http://s0lus.tumblr.com/post/43556201458
Spread
The humor made the post popular and bloggers started adding their own animated .gifs in response asking for a continuation of the comic strip. Some times the new cells would be drawn by the user adding the .gif and other times they would be added by other Tumblr users.