Lisa: Hey Otto, what are you doing?
Otto: I dunno, I just got this craving to join the navy. Yvan eht nioj! (gets on bus)
It is a means of subliminal messaging
used in THE SIMPSONS on barts boy band pop song DROP DA BOMB
three skinny women dance and sing the phrase yvan eht nioj
Lisa "wait lets play this backwards"
TV "Join the navy"
Lisa "Subliminal messaging!!!"