The thing is, Parks, is that it isn't a "joke" play. There are hysterical lines, such as the one you mention, but they're not jokes per se. They're taking an already absurd situation and pushing it to its completely illogical limits, and because of that, it's a riot. During the whole scene where Jack is interviewed by Lady Bracknell and the discussion of his supposed abandonment comes up, he points out that the place where he was left was on the Brighton Line, with the implication that this is a truly good (read "upscale") rail line. Her response -- "The line is immaterial!" -- in context is incredibly funny, even though I'd be really hard pressed to tell you why. It just is.
It's a shame we dont have folks who toy with the language with the same style Wilde did. It's tough writing because in order for it to work, you have to make it sound like it was passed off as a slight bauble of a
bon mot. That's hard to do. Probably the closest thing we have (or had, rather) is WHAT THE BUTLER SAW and almost anything from the early career of Tom Stoppard (from the days of JUMPERS and TRAVESTIES, before he got too serious about himself).
"That duck was a sexual toy, and it was on display!" -- an unknown Nashville town leader