You were lucky if there was only one! I recall teaching Pythagoras' Theorem and introducing the word 'hypotenuse', the most obnoxious boy in the class called out It's Harry Potter's pubes, and I couldn't prevent myself from laughing, The trouble was every year after I got the giggles at that lesson and most classes could persuade me to tell them why, some were shocked that i knew the word 'pubes'.