|Spoiler Inside: Solution to Puzzle||SelectShow>|
This is actually rather an easy problem, because the different letter requirement knocks down the number of possibilities. For example, Carl can not have the cat or the cheetah. In fact, each triplet of person, pet type, and favourite wild animal must have one item whose spelling starts with C, one with D, and one with G. Denise likes taking her pet for a walk. Her pet must be a cat. (OK, not so likely as a dog, but a goldfish is right out.) From this, the problem falls apart.
The solution is Carl-goldfish-dingo, Denise-cat-giraffe, Geoff-dog-cheetah.