APRIL the first or not, I wasn't going to let my sisters make me look a fool.     Lots of people were at Whipsnade Zoo to see us, 'cos we're three months old and were on show for the first time.     Dusty and Sandie - my name is Herman - and we're all named after pop stars - tried to gobble all the milk.     So I clobbered them, but our handlers spoiled the fight - they must think they're Goldilocks or something.     Still, it's no use crying over spilt milk.