King Willem III of the Netherlands was also known as King Gorilla, although saying it at the time would have ended you up in jail. Zürich (CH) police has a file on him that he used to walk out onto his balcony of his Zürich home only dressed in his morning robe and that he exposed himself to people passing.

King Willem II was our hero at Waterloo. He was one of the table guests of the Duke of Wellington at the yearly veteran's dinner in Apsley House. See also this picture of the young Willem II, then only the Prince of Orange.
www.flickr.com/photos/govert1970/2206963319/