I'm freelance but clients past and present have acquired names along the way.
There's 'Hyacincth' ...
Fake OTT loud posh voice, always manages to mention her 'Mercedes' in every conversation, as in "Sorry I did call you back earlier but I had to collect my Mercedes which was in for a service" and orders her poor hapless husband around (they are also business partners) so he's terrified to make any decision without deferring to her.
Then there's 'Gollum' - a slimy, revolting little runt of a man, who kept putting his hands on top of mine on the table at our first business meeting. When I pointedly pulled them out from underneath and then kept them under the table, he started touching my shoulder, arm etc. I was about five minutes away from smacking him in the mouth. I actually refused to work for him in the end.
There's 'Mr Bean' an utter prick of a man who has the biggest ego of anyone I've ever met, but in reality is this Mr Beanesque character and even looks a bit like him. Mr Bean and Gollum are good friends, and I refuse to work for either of them, although funnily enough I still work for the company. Just refuse to have anything to do with those two and the company accepted it!
Then there's Velma out of Scooby Doo - because she looks exactly like her, dresses like her, hairstyle, glasses etc. Velma has an ego nearly as big as Mr Bean's but not quite!!
One of my favourite clients is Captain Mainwaring. He's lovely, but I call him that because he's the spitting image of the Arthur Lowe character in Dad's Army.
Needless to say - I never actually call any of them these names out loud. It's just how I think of them.