I just made this up
Said by 90% of contributors to Urban Dictionary after submitting their description of peculiar sexual acts that only exist in their own imagination, as the definition of some concocted word or phrase, which they just made up.
The definition of diddly-doodly-doo is when you are having sex with a giant pile of spinach while playing video games and then your sister comes in and shoves the spinach up her vagina and you take a picture of this and post it on the internet and people in Bangkok get erections from looking at it. I just made this up.