with sign languages, the sign is not necessarily arbitrary. which can lead to hilarity.
i stumbled on this from a "don't click here!" link on mgoblog today. i'm a little embarrassed to say that i enjoyed it quite a bit, and there are several other related videos on youtube.
the performer is David Armand, in character as Johann Lippowitz. this was recorded in 2005, so don't get upset with me for being behind on my memery.
this also reminds me of the "fake language" videos going around youtube last year (which seem to have all been taken down since). in those, the best you can do to fake a language is try to make up nonsense words that accurately reflect the phonology and prosody of the language, but with fake sign language you can actually put some semantic content into the mix. just think about it: it's possible to "translate" an English song into fake sign language, but it's impossible to translate ASL speech into fake English!