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It turns out that ‘b’ is character number 98 in ASCII. So you can typeset the word bubble in a strange way by putting
       \char98 u\char98\char98 le
into your manuscript, if the b-key on your keyboard is broken. (An optional space is ignored after constants like ‘98’. Of course you need the \, c, h, a, and r keys to type ‘\char’, so let’s hope that they are always working.)
这是大师的幽默吗。。。