While that is a very good picture of irony right there (shame that PBF has irregular updates), I seem to have derived my conundrum from a difference source, but this example should suffice:
http://www.brawlinthefamily.com/comic157.html
While it is the dentist informs the patient that he is about to "clean his [the patient's] teeth", one initial audience response would immediately think that the dentist would be thinking of performing physical assault on the patient. The other would be inclined to think that the dentist literally does clean up the patient's teeth. The last one would be that the audience would expect anything, including non sequitur humor to occur.
In all three scenarios, according to the poor-technical definition of irony above, they all satisfy the irony presented in the story. I guess that that is the beauty of clever writing - to entangle the threads of double entendre and [double] irony into such a scenario.
Maybe I have been overlooking and analyzing simple literary devices and I should enjoy them for what they are. Thank you, Kraco!