Our Anglo culture does not always understand the German sense of humor. The best (satyrical) summary I've ever seen is from "The Xenophobe's Guide to the Germans", which says: "The Germans take humor very seriously. It is no laughing matter." It's a good way to describe it.
I can speak the language quite well now, but it is hard for me to keep up with a comedian (they speak very fast, with lots of slang). But hanging out with guys from work, I have learned that the humor is often quite directed -- they laugh "at" as much as they do "with". And, as usual in the German culture, there is not a lot of subtlety to their humor... but when they do put together a skit or a prank they approach it like building a BMW. All out. As you'll see below.
Here are a few pranks from an old television program, "Verstehst du Spass?" ("Do you understand fun?"). In the first, they set up a fake waterbed in a department store... and you know how everyone likes to try out beds (especially at 1:26 and 2:19). The targets take it pretty well.
In the second, they use identical twins and a fake bathroom mirror to make other visitors think they don't have a reflection. I especially like the end, where the girl has to remind her reflection to come with her (at 6:03).
The third skit is the longest and most complicated, but it's really worth it. A guy is driving someone else's BMW, and thinks it rolls down the hill and sinks in water. But then another guy drives a car over the same water, trying to convince him that it's just a large puddle (at 4:13). There's even more, with a disapperaing person in the same "puddle" (at 5:07) - it's worth the time to see the whole thing, even without the benefit of understanding the language.
Finally, I have to share this classic. It's not a prank, but a television commercial for Germans to learn English. A German Coast Guard rookie has to help a ship in distress... Cheers.