What do the following words have in common?

CASE
CLOD
COLD
DRESS
FRY
MOTH
ONCE
POND

HINT:
The same letter can change each word into a new one.

Answer:

The letter U can be inserted into each word to create a new one:

CAUSE
CLOUD
COULD
DURESS
FURY
MOUTH
OUNCE
POUND

Credit: LA Times Crossword
Sylvia Bursztyn and Barry Tunick
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