When I went to the dealer...
the most surreal story of sh*t they do other than fix the bloody problem wins

Here are mine.
...they gave me a £50 car wash.
This was 5 years ago. There was a £50 charge for their diagnosis of "nothing is wrong". I was convinced that something was wrong, so I took it to a normal mechanic who found the throttle position sensor had a flat spot.
...they told me off about the about the wear on my tyres.
This was last week when I got a new immobiliser aerial. Besides fixing the problem, they decided to measure the depth of the treads on my tyres (3mm all round) and gave me a stern talking to about how they might not last for long. Why on earth would they waste their time measuring my tyres? I just cannot apprehend rightly the confusion of ideas that connects "fix the immobiliser" with "check the tread on the tyres".
...they put my name up on a poster.
This was also for the immobiliser incident. I went to pick up the car, and they had a poster with a list of names of all the customers they were expecting to pick up cars that day. Just bizarre.