1. What do the following three-letter words have in common?

FIB
MET
SHE
SOB
WAG

2. What do the following words have in common?

APE
MAN
LATE

Answers:

1. Each word can be changed into a new one by adding ER at the end:

FIBER
METER
SHEER
SOBER
WAGER

2. Each word can be changed into a new one by adding X at the end:

APEX
MANX
LATEX

Credit #2:
NY Times Crossword
October 13, 1996
Wayne Robert Williams
SOMETHING EXTRA