Doctor Clarke always stopped at his local pub after work for a hazelnut daiquiri [a special drink the bartender created just for him].
One day, Dermot, the barman ran out of hazelnut flavour so he substituted hickory nuts instead.
Doctor Clarke took one sip of the drink and exclaimed, 'This isn't a hazelnut daiquiri. Dermot!'
'No, I'm sorry', replied Dermot, 'it's a hickory daiquiri, doc.'