Because Thurl Ravenscroft was not credited in the closing credits of the 1966 television special as singing the song "You're a Mean One, Mr. Grinch", it is sometimes attributed to Boris Karloff. After becoming aware of this oversight, Seuss himself called Ravenscroft and apologized profusely and later wrote letters to columnists nationwide telling them that it was Ravenscroft who provided vocals for the musical number.
Since Thurl Ravenscroft was not acknowledged in the closing credits of the 1966 television special as singing "You're a Mean One, Mr. Grinch", it is occasionally attributed to Boris Karloff. After realizing this mistake, Dr. Seuss contacted Ravenscroft and expressed deep regret, and later wrote letters to columnists explaining that Ravenscroft provided the vocals for the musical number.