From George Carlin:

Sometimes I leave stuff too long in the fridge...check this out:

Could be meat....
                  might be cake...!

When I'm worried if I'm possibly eatin' stuff gone bad, I recall that episode in the Aubrey Maturin series where the cap'n and the doctor remark to Killock that the coffee seems off. He tells him that rats broke into the coffee supply so there were a lot of rat turds mixed into the grounds. They go on to drink every drop. That's the power of coffee.