"Blodgett—Elexander Blodgett—Reverend Elexander Blodgett..."
See in text (Chapter XXIV)
Notice the em-dashes in this sentence. Twain uses them to elaborate on the lie the King tells and emphasize that he's making it up on the spot. It's clear, from this construction, that the King wasn't intending to impersonate a reverend at the beginning, but that the idea came to him after he'd already fabricated a very official sounding name and taken into account his very proper attire.