Mood Rings

     Mood rings are halo-like in appearance, and are invisible to normal people without the right magical spell or tool. They fall gently from the sky and find someone's head (not that they will notice), which they will gravitate toward and float over once found. They were made by a deity who intended to spread positive feelings throughout as many realities as it could, which required that they sacrifice their existence to do so (lest they never make a significant impact anytime soon).

     Unfortunately, the results are often an example of paving a way to Hell with good intentions. With the deity's demise, they couldn't tailor the rings for every individual, so they affect people randomly. The deity hadn't minded that, though, because they were of the mind that the existence of the positivity was what was important, not how it affected anyone's life.

     Whoever ends up with a mood ring could feel various positive things (interest, excitement, joy, contentment, arousal, et cetera) about practically anything, even if the individual in question normally had a strong negative response to it before. On top of that, the mood rings have a positive-reinforcement effect, so they can have lasting effects if not removed quickly enough.