1 {scene: inside the Classical Museum in Tripoli}
1 Monty: According to this Ancient Greek inscription, the Gorgons' lair is this way.
2 Prof. Jones: Wow, look at all of these incredibly lifelike statues.
2 Prof. Jones: Oh! You know, these could be people who came to look for the Gorgons and...
4 Monty: Succeeded... {looking at statues of Colonel Haken, Erwin, and Ginny}

It's really tedious making the figures grey like that. Not difficult, just tedious, because I need to trace over the figures carefully in Photoshop, so the strip ends up taking about 5 times as long to make as normal.

EDIT: Thanks to the many people who suggested it would be easier to get this effect by shooting two shots, one with only the figures to be turned grey, and one with all the rest of the scenery, and then doing green-screen magic in Photoshop. In fact, that would be considerably more work than the way I've done it. Trust me.