Bug's Bunny is one of the most iconic cartoon characters of all time. He is a white rabbit who is known for his catchphrase, 'What's up, Doc?' and his mischievous behavior. He first appeared in 1940 in the Warner Brothers animated short 'A Wild HARE' and has since become a beloved figure in popular culture. His name is a play on the phrase 'HARE-brained, ' which is a reference to his mischievous nature. The crossword solution for the term 'BUGS BUNNY IS ONE' is 'HARE, ' which is a four-letter word that refers to the type of animal Bugs Bunny is.