Most of the candy forest set in the original Willy Wonka and the Chocolate Factory was actually edible!
Talk about dedication to your craft. The director wanted to make the kids' reactions to the movie set as realistic as possible. The big candy forest set with the chocolate river was built to be realistic and completely edible. The chocolate river was real, the giant mushrooms were filled with whipped cream. The trees had actual chocolate.
The director wanted the kids and parents to have such a realistic reaction that he didn't let them see the set until they filmed them looking at it for the first time. One funny thing is that the cup that Gene Wilder bites at the end of the song was actually NOT edible. He spat out the wax he bit off. It was soon replaced by a sugar one.