I found that resource I was talking about--where you can add certain things to beers to imitate off flavors. First off, the resource is "Radical Brewing" by Randy Mosher. GREAT BOOK.
He mentions 12 common off-flavors and aromas:
He describes each one in detail, but in some cases he suggests a sample of a certain "ingredient" to add to replicate the aroma or off-flavor. I've included some common ones. These are not directly quoted, I've abridged them to save this post from being 347 pages long.
ALSO--he emphazizes the samples that are spiked should be sniffed only, NOT CONSUMED!
1. Acetaldehyde-Common chemical recognizant of green apples, sometimes indicating an infection. Smash a green apple jolly rancher candy and soak it in a little water overnight. Add to a sample beer.
2. Acetic- A vinegary aroma caused by infection--use a couple of teaspoons of distilled vinegar in a sample of beer.
3. Diacetyl- Produced by yeast if temp becomes too warm in fermentation. Some beers it can be desirable in low concentrations, but it is generally regarded as a defect if it sticks out too much. one to four drops (or 1/8 tsp.) of butter flavor extract (used for baking) to a sample beer.
4. Di-methyl sulfide- A vegetal aroma that results from a weak boil,or a slow yeast start. Add juice from canned corn to a sample of light beer.
5. Oxidized-A papery, wet cardboard aroma, the result of overaged beer, enhanced by overexposure to air during the brewing process. No recommendation on what to add to a sample of beer, other than finding the oldest dust covered beer you can find, and smelling it. I'm convinced this is what I had in my first Brown Ale batch. I think the wort got oxidized and it had that cardboard smell to it.
6. Phenolic-Indicator of wild yeast infection, and smells like an electrical fire. He suggests smelly a burned circuit board for an example. Don't dunk it in beer, just smell it!
7. Skunky- Result of light hitting dissolved hop compounds. He suggest setting a European beer in the sun for an hour, chill and serve. I say just buy a Corona.
8. Solvent- Esters produced by yeast at higher temps, which contribute floral or fruity notes to ales. Put a few drops of nail polish remover (non-perfumed kind) in a beer. Smell.
Anyway, I found these intersting, and it would be a cool experiment to do with your brewing buddies someday.