<human>: To start this happened a couple of years back. 

I was at my ex-gf's and was helping her do laundry. Took out dry laundry from dryer, bunch of ex-gf underwear was in the load. Decided that I am a comedian and could get a good laugh from her by wearing one of them on my head. Like 5 seconds later her 18 year old sister walks by and sees me with bright red panties on my head. I stand in shock as I see her staring, knowing that shes looking at the dumbest person she has ever seen in her life. She then asks "What the hell are you doing wearing my panties on your head?"

At this point I knew all was lost. I stood staring for eternity. It was probably 2 seconds but holy hell it felt like forever. I just reacted out of survival instincts. I threw it at her direction and it hits her in the face. I just made it even worse. She just stood there, mouth open. I think she started saying "WTF is wrong with you" but I was already running out of there straight to the ex gf's room. I just slam the door close and sit on a chair in front of door (protecting myslef? I have no idea I was still clearly not thinking right at all).

GF didn't find out until later that night. Fighting ensued. I did not win.  

I still think I'm hilarious though.

Provide a brief overview of the text.
<bot>: Put ex-gf's sisters panties on my head by mistake, got caught by her sister, have now gotten in both their panties