Query: How are "literary cameos", following the examples brought up by the wikipedia summary, to be distinguished or categorized among allusions, quotations , watermarks and references to "Sirin" as they were inserted by Nabokov in his novels?  Would Lolita represent "the apex of the technique"?

 "A cameo appearance can be made by the author of a work to put a sort of personal "signature" on a story [   ] At the apex of the technique stands Lolita by Vladimir Nabokov. This acclaimed novel is, among many other things, a "tour de force" of literary cameos. "