Not so much inside jokes since they're pretty obvious, but one of the things I like about products designed for small, geeky user bases is their frequent use of ironic jokes. The FMR RNP preamp ("RNP" stands for "Really Nice Preamp") has in/out jacks on the back labeled "Guzintas" and "Guzoutas" (see above); the headphone gain knob on the Presonus FP10 goes to (you guessed it) 11.

They're not even really good jokes. And they're typically very small or otherwise obscured. The RNP panel above is on the back of the box; the label on the FP10's headphone knob is so tiny you have to squint to see it. Which (to me anyway), shifts them from unfunny into funny somehow. Or maybe it's just that they were so expensive (for my budget) that I'm looking for some reason to believe they're more sophisticated than they really are (or than I really am).