Two six-letter words differ by only a single letter. The first word names one of a group of twelve. Change one letter in this word by moving it one place forward in the alphabet and you will have a word that names one of a group of eight.

HINT:
The letters that change are the first letters of the two words.

Answers:

CANCER  (sign of the Zodiac)
DANCER  (Santa's reindeer)

Credit:
NPR Weekend Edition Sunday Puzzle
October 16, 2011
Will Shortz