I took over a pack 5 years ago that had a horrible standard of uniforming. I was dismayed by the boys and leaders who came to meetings not in uniform or in totally inappropriate uniforms such as the one mentioned at the start of this thread.
I tackled it on several fronts. First, I felt that it would be too intimidating for the Cubmaster to pull any individual Cub aside. So I challenged the Den Leaders to raise the bar on their own uniforming as well as their dens. This helped, and we saw some immediate improvement.
Second, we had periodic surprise uniform inspections at Pack Meetings. They were done as the boys came in. It was a simple checklist - neat appearance, proper uniform shirt, belt and hat, clean jeans or slacks, proper insignia sewed on (I get so tired of kids wearing two years of rank advancments on safety pins!). We recognized the dens that had the best score, but did not point out any individuals (for good or bad uniforms).
Third, we did a form of the skit that was mentioned. But we didn't use any outrageously bad uniforms. I just inspected the leaders and pointed out what they did good or bad (and they, in turn, inspected me). It was good for a laugh or two.
Over the period of 6 months or so, we saw a tremendous improvement. However, most of the improvement came from the younger Cubs. The older ones were accustomed to the bad habits, and were harder to change.