Whenever I see coconut milk on sale, I stock up a few cans, regardless of the brand, thinking that they should be fairly similar.
So I pull out one can each of two different brands, since the recipe for Coconut Rice Pudding called for 2 cups and each can is 13.5 oz. Upon opening them, I discovered the thickness of one brand was like that of creme fraiche while the other brand was much more like coconut milk; a somewhat watered down whole milk. Reading the labels, which is what I should've done before buying, I found that the thick coconut milk was coconut extract, water, and "thickeners", while the other actually said "coconut milk".
So I mixed the two, and had to alter the cooking time to adjust for the thickness, which is normally obtained through the cooking.
Lesson learned!! Get the real stuff!!