A STREETCAR NA_ED DESIRE
We don't know who Kevin is or how well versed he is in the combined oeuvre of Tennessee Williams, Marlon Brando, Vivien Leigh, or Elia Kazan. We don't know if Kevin knew the legendary 1947 play and the classic 1951 film A Streetcar Named Desire. We don't know what dark clouds in Kevin's mind possessed him to turn an exceptionally simple hint into a grammatically incorrect sex joke...but here we are.
On his turn, Kevin guessed the missing letter was "K!" -- as in "A STREETCAR NAKED DESIRE."
The rest is history. The audience groaned. The buzzer blared. Lisa, the next contestant, got it right. Twitter exploded.