I have occasionally heard it said that it is the things that are true that are the most funny. I think this kind of statement doesn't quite say what it actually means; rather it derives from something different. When people hear a joke involving something they themselves have experienced, the comment ``That's so true!'' is frequently made, though it's not truth so much as personal experience that's involved. These jokes are often said to be the funniest, in some sense. This follows: if the violation is made clear in the joke, and it relates to something the person has experienced, then not only does the person interpret the normal event depicted in the joke as being funny, but also they interpret their own experience as funny. Seeing the violation in yourself is like having the joke told twice, and better the second time, because the funny situation is not just in the joke but in your own experience.
Self-deception has an important role here. People often try to normalize their experiences. ``Things are really okay, even if this seems a little strange'' is the underlying refrain, which may not be self-persuasive successful in all circumstances, but is sufficiently successful in deceiving oneself that some unacceptable things are accepted as normal. Then at some later time a joke may be heard in which relevant aspects of the same kind of situation are portrayed and perceived both as normal and also as a real violation of the way things ought to be. The portrayal of the violation has the effect of converting one's normalized experience into something also seen as a violation of the way things ought to be. Thus the experience itself and one's affective involvement in that experience are converted into a source of humor. That is, it is not just the depiction in the joke which is N and V simultaneously, it is one's own experience which is seen to be N and V simultaneously. This is what people mean, I think, when they say that true jokes are the funniest jokes. Note that neither is truth essential (it's personal experience rather than truth) nor are these jokes necessarily actually the funniest. Greater volume and duration of laughter, for example, may well occur in jokes that aren't ``true'' in this sense. Nonetheless it is clear that such ``true'' jokes have extra ingredients that give them increased intensity.