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.
Thurl Ravenscroft was not credited in the closing credits of the 1966 television special "You're a Mean One, Mr. Grinch", which led some to mistakenly attribute it to Boris Karloff. Upon becoming aware of this oversight, Dr. Seuss reached out to Ravenscroft and apologized profusely, clarifying that Ravenscroft was responsible for providing the vocals.