There was a mum and her daughter in the zoo and the little girl sees two monkeys having sex and she goes:
'mummy what are they doing?'
'they're making cake' said her mum
then they went to the park and saw two teenagers having sex and she asks:
'what are they doing?'
'they're making cake' her mum said.
the next day the girl goes up to the mum and says 'you and daddy were making cake last night weren't you'
'how did you kow?' asks mum
'because i licked the icing off the sofa' she says.