when you are in a blanket all day and refuse to leave it
or
when people used to play guitar hero and covered half their screen with a blanket to form a false hyperspeed
"yo imma go blankie mode"
"it's better with a heated blanket"
"that's why I have one."
"fuck it, blankie mode time"
*proceeds to cover half the screen with a blanket*
"ah, perfect"
Yankie Blankie refers to the dexterous process of masturbationdone under any type of fabric layer (such as a blanket) in which it is preformed by either yourself or someone else.
I was flying home from a boating trip at sea when the person I was holding hands with slowly put my hand on his junk that was stealthily hidden underneath a blanket where I then proceeded to give him a yankie blankie