One thousand people all agree that "something" is positively the funniest thing they have ever seen/heard. Along comes Jack who the thousand also agree is the funniest with the best sense of humor. They let Jack experience the "something" and for some inexplicable reason, he finds it unfunny. Three days later Jack dies laughing over the same thing.
I love "Blazing Saddles." It ranks as one of my Top Ten movies and yet the first time I saw it, I never laughed once. Nothing was bothering me, I felt fine, etc. Someone wrangled me into seeing it again on a date and I couldn't stop laughing. I was literally on the floor of the theatre at one point.
Steve Allen wrote some great stuff on this subject concluding that he too had no idea.