Some of the hygiene things? Yep - it happens, but then the aircraft environment doesn't lend itself greatly to hygiene anyway - you pays your money and takes your choice. None of what i've seen is malevolent, but then again nor is ending up witih twigs in your beans when you go camping.
But for the other stuff - maybe it's happened once somewhere in the dim past, after all, the number of flights each day, each country ... vast.
But to suggest that this is prevalent is ridiculous, and to add my penny - i've never seen it, nor heard of it going on (and one can get quite frank opinions downroute after a couple of beers) - even if a skipper (or FO for that matter) has @rsed someone off big time. Apart from Lankey. But that's another rumour....
So MOR, I'd call your bluff on this one - I reckon you're (a) making it up for effect, (b) not who you say you are <delete as appropriate>.
Back before 11/9, when the doors were open, we'd be in an out of the galleys all the time - and I'd have thought that someone somewhere would have made a few big issues if this sort of thing was rife.
It's not - although not saying it's never happened - but it's not.