What do the following words have in common?


RAIL
ROCK
MARK
RIVER 
DIARY
COSMIC
DONATOR

HINT:
The title of this puzzle is ALIEN ABDUCTIONS.

Answer:

The letters ET can be added to or inserted into each word to make a new one:

RETAIL
ROCKET
MARKET
RIVETER
DIETARY
COSMETIC
DETONATOR

Credit: NY Times Crossword
February 28, 1999
Dave Tuller
ALIEN ABDUCTIONS