In grade school, I recall there being more than one occasion when I slapped a friend in the back of the head for such instructional purposes when he became too solipsistic. (this wouldn't disprove solipsism, of course, but it would imply a "masochistic solipsism", and it turned out he strongly preferred realism over that)

In hindsight I wonder why he remained such a steadfast friend, and now I wonder whether, if I had ever had a banana handy, that would have been the last straw.