A man goes to the circus , he gets a front row seat and the show begins , on come on the clowns and the lead clown comes over towards the man and starts to play to the audience "Whats worse than being the front or rear end of an ass? ......"No end of an ass" and the clown points and parps his horn with confetti over the man , the audience erupts with laughter and the man is mortified with embarrassment at the belittling he endured . 

 The next night the man goes back to the circus and gets another front row seat , sure enough the clown leader comes in and goes over to the man again , as the man gets ready to say something the clown takes another horn out and sprays him with water , while the audience is laughing at this he pipes up again "Whats worse than being the front or rear end of an ass? ......"No end of an ass" and the clown parps his horn with confetti over the man again  , and as the first night the audience erupted with laughter . The man can hardly contain his anger over the embarassment and goes home .

 He gets out the Yellow Pages (Google on paper) , scans through it and finds what he was looking for ...the number for Professor Darren Humphries world famous `Grand Master of Comeback Lines and Witty Repartee` , he contacts the Professor and details his woes and he agrees to help him . The next night the Professor goes to the circus dressed in disguise as the man and purchases the same front row ticket as the man , the shows starts and the clown sees who he thought was the man , ripe for humiliation again . The the clown comes up to the Professor , expecting to deliver the same treatment to the man again and starts "Whats worse than being the front or rear end of an ass? at the last syllable the Professor stands up and rips off his disguise , the whole crowd turns and gasps as they recognise the world renowned Professor as the Grand Master of Comeback Lines and Witty Repartee , they hold one universal breath , the clown is agape with shock as the Professor opens his mouth and shouts "Fuck off you red nosed twat" . 

I love the joke for a few reasons , it makes me laugh , its a good joke to tell when drinking and shouting the punchline but also the secondary point of the joke is that sometimes wit and sensibility take back seat and the best answer is full-on swearing (ahem certain threads) .