Everything is relative to perception, and your perception is limited.
The Ginger Ninja
A stunned investigator can be moved by any mythos or action card effect because the stunnig effect only affects their movement steps.
For monsters the rule says it may not move or attack. But can it be moved with Pete's guitar?
That's a great question. I'm not sure if that has been clarified anywhere. Seems like a rule and move on kind of thing, but I suppose thematic arguments can be made for days.