The answers to each clue below will have something in common - unrelated to the clue itself.

1. Slot machines, informally
2. Ecstatic, as in "Feel like .........
3. Some gold diggers
4. Condition specified in a Beatles song
5. Clio, Thalia, and their sisters
6. OTC drug taken by many for cardiac health
7. Common quantity for boxing small items
8. Two bits, formally

Answers:

1. One-armed bandits
2. Feel like a million bucks
3. Forty-niners
4. "When I'm sixty-four "
5. The Nine Muses
6. Low-dose aspirin (81 mg)
7. Gross (144)
8. Twenty-five cents

What they have in common:

Each answer contains a number that is a perfect square.

Credit:
NY Times Crossword
Harvey Estes
PERFECT SQUARES