The big white statue of a dog in Noelle Winters's apartment is the same statue that Chandler and Joey (and later Chandler and Monica) own on Friends (1994) (1994). It might be a similar looking dog statue, but it's not the same one as the one on Friends, since that one belonged to Jennifer Aniston in real life.
On the show Columbo (1971), also about an eccentric yet brilliant detective whom people underestimate upon first meeting him (until realizing he's brilliant), there is also a Playboy-magazine-inspired episode. Also, like Peter Falk, Monk gets very shy about seeing naked women.
Danny Bonaduce will be mentioned in Mr. Monk and the Paperboy (2004) (#2.10). Kevin Dorfman talks to him on the telephone. Both have the suffix "boy" in the title.