Which DIY project turned out surprisingly well—or went completely wrong?

Hey everyone, which DIY project were you sure would be easy at the start—and then either turned out really well or completely went off the rails?

For me, it was a homemade shelf: The plan looked solid, but in practice one side panel was crooked and, of course, the cut boards were oriented exactly the wrong way. In the end, it’s still sturdy and even looks better than I expected. What have you experienced—feel free to share your biggest mistakes and little successes, too!