Season 4, Episode 8: "Wishful Thinking"
Writer Ben Edlund has a gift for finding humanity in even the most absurd places. In "Wishful Thinking" a wishing well actually works, but as with most things in the Supernatural world, there is a downside. You know, just small stuff like a teddy bear having a super dark existential crisis or a kid's newfound superstrength going to his head. There's a lot of wackiness in this season four gem, but it's brilliant wackiness that pays off with a heartbreaking confession from Dean before the hour's over.