Spoonerising madness

A couple of my mates work in the same place - a suit-and-tie car
dealership - and they both appeared at my shoulder last night, gagging
to tell me about their colleague. This chap had just come in from a
frustratingly fruitless punter pursuit around the wet and windswept
forecourt and was just about to make a derisory comment on the weather,
when he saw his (female, twinset-wearing) boss approaching.

So, he changed his words that were already almost out of his mouth and
promptly performed a wonderful verbal train crash by altering "It's
fucking disgusting out there" to:

"It's ducking fistfucking out there".

Apparently he had carpet burns on his knees when he was released from
her office - and not in a good way.