It's a rather fast song, so even if John could read the French, the words were flying by so quickly on the screen he would barely have been able to sing along (which also happened on the Fu Fighters track). He ended up basically making up words and singing in a horrible nasal tone that was supposed to approximate French; Hannah and I laughed so hard I thought she might wet herself. And to top it off, when his score came up and he had a chance to add his name to the high-score list, he was perturbed to find that he was only number six, since none of us had ever done that song before.
I think Hannah is the only one of us before last night that has played Rock Band alone as a singer, but I never payed attention to the avatars while she was singing (which is basically the only time you get a clear look at them without the guitar/drum line in the way). The only reason I payed attention last night was that I had recently read that Courtney Love was pissed about the way the avatar for Kurt Cobain had turned out for Guitar Hero.
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Hannah has always commented on the appearance of the avatars--"Get a haircut, hippies!" (I think she's channeling Richard Nixon)--but I just noticed that one in particular bears a strong resemblance to a character from The Dark Crystal:
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"Hi, I'm a Gelfling!"
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Uncanny, no?