I'd like to FPP that to MetaFilter in February, but I have a feeling that would get me permabanned. Don't dislodge the complacency!
Though I think my idea of "Talk in Character Day" is a nice alternative to "Talk the way we tell you to talk" day. You get to be wacky and celebrate creativity. TLaPD is like a National Joke Day where everyone has to tell the same exact joke (yes, I was that kid who when everyone else was playing Cowboys and Injuns had to be an android or something). And I often have to stop myself from talking in a given accent; it'd be nice to have a day where I could be faux Scottish the whole time. Or Jamaican. It'd be like Halloween without costumes (FYI, tops on my list of Halloween peeves is people who dress up but totally fail to even pretend to be in character for even just a little bit of the day). And it'd be a great chance to learn about stereotypes of other people's cultures!
So yeah, see also here, here, and, if you're bored, here.