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So, I was doing research, and the source for this name seems to be Japanese Wikipedia, which lists this enemy as キラーチェアー (kirācheā, Killer Chair), it also lists Mad Piano as キラーピアノ (kirāpiano, Killer Piano) and Bookend as キラーブック (kirābukku, Killer Book), which is also the name TMK gives (they also seem to be our source of the "Bookend" name). Binarystep (talk) 02:42, 21 April 2015 (EDT)

For what it's worth, I have the DS Pocket Guide (which is the only official guide for SM64 DS), and it doesn't seem to mention chairs at all, though since it calls the Mad Piano "a vicious piano" and the Bookends "books", I wouldn't have high hopes for the Killer Chairs not just being called "chairs". Hello, I'm Time Turner.