1

I've always used them interchangeably according to my mood.

But are there any rare cases where they aren't interchangeable or have a slightly different meaning?

2

Anyone and anybody have no difference in meaning. Anybody is a little less formal than anyone. Anyone is used more in writing than anybody.

Anyone, anybody and anything (Cambridge Dictionary)

  • so is the case with someone/somebody, everyone/everybody and no one/nobody – user88834 Mar 11 '19 at 16:55
  • yes, I think you could say the same about those three word pairs. – Mixolydian Mar 11 '19 at 18:57