Fingers in his ass originally was a joke from both the undertale and danganronpa fandoms and features the characters Sans Undertale and Nagito Komoeada.
“Fingers in his ass, fingers in his ass, Kanye west he likes, fingers in his ass.”
The act of sticking a soda bottle lid in someones rectum, and putting the tip of the bottle up the anus. Turning the bottle till the lid is firmly tightend will conclude the act.