The following crossword clues and their answers share a very unusual quality. Can you determine what it is?

1. SHAZAM!
2. Haphazard
3. M*A*S*H star
4. Flashbacks and halfbacks
5. Half an Xmas "Halls" chant
6. Astral saga that has a Darth part
7. Grand-slam drama that stars Bacall's man
8. Fab "backward-gram" a la "Sam aha! Bahamas!"

HINTS:
#1: For the unusual quality, look carefully at the letters of the clue words.
#2: Specifically, notice the vowels in the clue words.
#3: This unusual quality should be a hint in determining the answers.

Answers:

1. Abracadabra!
2. Catch as catch can
3. Alan Alda
4. Anagrams
5. FALALALALA
6. Star Wars
7. Casablanca
8. A man, a plan, a canal, Panama

Unusual quality: The only vowel used in both the clues and the answers is A.

Credit: NY Times Crossword
Andrew Chaikin - Jan. 12, 2014
IT'S ONLY "A" GAME