The word facetious is one of a handful of words in the English language that has all the vowels in alphabetical order. Another is abstemious. Other less common words that fit in this category include acheilous, anemious, caesious, annelidous, and arsenious. If you add an "ly" to the end of these words, you get all the vowels in order, plus the sometimes vowel "y".
More facts about English words: