This one's sanity must've already crumbled...

This sentence is often used when someone is acting unusually silly or crazy.

Originally refers to the roguelite roblox game Deepwoken. In-game it is said by one of the ignition union members after facing akira in the depths and being told to back off even though they outnumber him.
Ultimately ending in the squad's death after they pass the line drawn by akira.