movie, song, a piece of art or something else that changed you drastically, made you basically a new person or heavily influenced the way you perceive world around you, other people etc.
Man1:I saw my grandmas pie and I can't get it out of my mind it's tattooed on my brain.
Man2: It's your memory so don't give it to me.
Man1:I wish the brain had an erase botton.