I don’t know if this is an urban legend or not. When I was around 10 years old I hear it.
There was a school play and they had a “marriage” scene. Two kids, over bar/bat mitzvah went up, said Harei at with others around and he handed her a ring. It was part of the plot. What I heard was it was paskened as a real wedding and they had to get an actual divorce of sorts…but there was no yichud afterwards so I don’t know how it actually went down.