In all the recent hype over The Muppets (sidebar: if you haven't seen it yet, GO!), it's interesting that most people seem to have forgotten completely about the short-lived ABC revival in the mid-90s called Muppets Tonight. Most of the articles about the Muppets have focused almost exclusively on the progressively weaker theatrical and made-for-TV movies that were produced after Jim Henson's death. Muppets Tonight was actually pretty witty, and unfortunately just didn't find its audience.
Below is one of my favorite sketches from the series and a good example of how the Muppet creators were adept at weaving in some humor that is aimed more at the older folk in the crowd than the young kids. The punchline to this scene is still one of the biggest Muppet-related laughs I've ever had. (Either click the link in the last sentence or go to 7:08 in the embedded clip below. For some reason I can't embed a version that goes directly to the sketch in question.)
And as a bonus, here's a little manufactured adult humor from the Muppets. It's called "The Song of the Count." I dare you not to laugh hysterically at this.