Fabnesia
A stupid trick you use to pretend you don't know everything about your friend because you're either a stalker or you're too lazy to come up with something real to say.
'You don't know they got a new haircut? I guess I'll just say I got a new haircut in my head.'
You didn't know your friend got a new pet? I guess I'll just say I got a new pet in my head.
You didn't know your friend got a new tattoo? I guess I'll just say I got a new tattoo in my head.