Telling this to someone is basically saying they are stupid.
Terry: Hey, Tables on bed!
Harry: How rude
Terry: *trips*
Harry: Haha, How does it feel to be Tables on bed?
"FAFBNFETRFTP" means you are very proud of yourself but deep down inside you are sad... Very Sad.
Walley: Welcome Dante to our group of top ranking students, you may put down your own alias or nickname so we may identify you.
Dante: "FAFBNFETRFTP"
Walley: What does your nickname imply? I bet it's like a family code you cherish knowing that you are proud of yourself.
Dante: No sir it means "Fast As Fuck But Not Fast Enough To Run From The Pain"
Walley: bro...
Dante: bro...