A.) After taking a poop and wiping your anus realizing your not done then taking another shit on your previous shit forming a double stacker.
B.)Purposely made double stackers occur when someone takes a dump then decides not to flush to come back later and dump on it again
Me: Man earlier i was taking a shit and I thought i was done, pulled my pants up then it hit me again
Q: So what did you do? tell me you didn't...
Me: Yep made a double stacker
Q: Thanks for sharing