Unless these pranks verge into physical harm, I suggest we simply correct whatever inconvenience they cause and move on with our daily routines.
I have seen the man in the garish white suit identified as "Elvis," a figure from Earth musical history and have seen glimpses of him myself, but he seems to be insubstantial and impossible to catch up to by all accounts. There is no evidence to suggest that he is connected with these childish pranks, or indeed that he is a threat at all.
It would be prudent to pay particular attention to your hygiene products--particularly the liquid ones such as soap or shampoo--before using them, as it seems these are the most commonly occurring incidents.