Castiel was confused by the human's need for sugary confections. Sure, he'd seen his brother Gabriel pig out on sweets, but that was his archangel brother. He didn't need the food. He just liked it.
Cas wasn't complaining - he was far from it - but he was slightly confused. And aroused. Which lead to all of the internal questioning. The angel didn't know what he found so attractive about Dean eating a lolly. All he knew, was that the sight of the blond hunter eating and licking the sweet, revealing his tongue to the dark-haired man, made Cas' insides tighten, and the angel felt a flush of warmth run through him.
Cas shrugged it off - angels couldn't feel pain, so he was in no bother - but kept a close eye on the blond, who had seemingly bought a years supply of lollies, and was currently pulling a new one out of his pocket, while they sat in Bobby's library, and Cas knew he was going to be able to do little to know work that night. And it was all Dean's fault. Well, he wasn't to know that, though, but he still was to blame.