This isn't a 'gig' blooper, but a brill one none the less, that I hope you'll agree is worth sharing. My husband is a lectuer at an agricultural college and he was in the staff room with a colleague who was looking at exam papers.

The question had clearly been something along the lines of 'How do you tell when a cow is in season and ready to take to the bull'.

The given answer by this, now immortalised student was 'Females on heat have red Volvos'!!!!