It’s a reference to 1 man 1 jar, a shock video that went viral about years ago.

Essentially, it shows a naked man squatting on a jar, which slides all the way up his ass. The jar then shatters, and the rest of the video is him trying to pull the glass shards out while clearly losing a lot of blood.

Feel free to seek it out if you are curious, but be aware you will see exactly what I described.