Jeph also makes some pretty savvy references in his strip, encompassing everything from Shakespeare to Indiana Jones to an FLCL-styled chick called the VespAvenger. In the earlier strips, a lot of the humor is directed at various indie bands. Those references go right over my head, but those who do keep tabs on the indie scene will feel very much in on the joke.
Some strips deal with personal issues the characters face at the time. Some strips simply do all they can to set up a powerful punch line. And some strips are clearly there because Jeph really wanted to draw them. For instance, comic #666 (subtitled "I've been waiting three years for this strip") includes a completely unprecedented and unexpected break in continuity for a "spontaneous metal interlude" where all the characters dress up like the spawn of KISS and rock out for a few panels before going back to normal.
One of the highlights of Questionable Content is the depth of the characters. While some webcomics tend to let their characters change personality at the drop of a hat to generate a storyline, Jeph does a fantastic job of developing his characters and sticking to the traits he assigns them. As a result, his characters seem truer-to-life and more believable than many webcomics. By the time a reader has made it all the way through the archives to the current issues he will feel as if he knows these characters, or at least knows people in his life like these characters.
Questionable Content is updated five times a week, Monday through Friday. In addition to the daily comic, the site contains Jeph's music suggestions, links to other webcomics of interest, and an online store which sells t-shirts bearing popular QC characters and slogans. Be forewarned that QC is definitely for mature readers. The characters are prone to strong language, generally in colorful and unusual combinations. While there is never any explicit sexual action, there is a lot of implied action, suggestive situations, and dialogue.
Jeph has kept the site going strong for over four years now, and with any luck it'll be around for a long time to come. Check out QC today and find out what all the hype is about.