EXTRA PLAY
Credit: NY Times Crossword
Alan Arbesfeld

What do the following words have in common?

SO
TO
ALL
BIG
ROB
BALL

HINT:
The same two letters, properly placed, will change each word into a new one.

Answer:

Adding the letters OT to each word changes it into a new one:

SOOT
TOOT
ALLOT
BIGOT
ROBOT
BALLOT