All right, I'll bite. Someone has to get this forum rolling.
I propose a small (four or five person) team go "street climbing", that is, mountaineer their way "up" a city sidewalk (as if the sidewalk were actually a sheer cliff) while a second small crew (three or four) acts as a Discovery Channel-esque documentary team recording their "ascent". It's not a long or in-depth mission, but it's fun and certainly bizarre enough to cause a scene.
Now while it's not precisely original, thirty or forty years does seem like enough time to let an idea incubate before repeating it. The Pythons originally did this as a skit, and I managed to dig up a Youtube link.
http://youtube.com/watch?v=9U0tDU37q2M&feature=related
I think the Pythons hit on a few key aspects that make this a really humourous situation, especially the odd juxtaposition of the sidewalk-bound climbers and the unaffected reporters treating them seriously. We'd need good speakers capable of keeping up a running dialogue for the interviewer and at least one of the climbers. Aside from that, the only real materials required are cold weather clothes for the climbers, a suit and mic for the interviewers, and climbing gear (or mock climbing gear, e.g. ropes around the waist) and a tent for the mountaineers.
