Elst-Pizarro is often misunderstood, as people have trouble knowing if it is an asteroid or a comet. This is not a crazy problem, but most experts can see the difference. Yet Elst-Pizarro just felt like being different. Discovered in 1979, we did not really care about it a lot as it was within the asteroid field. By 1996, it was showing a tail like a comet. This led to many just assuming it was debris from a collision.
However, the tail’s brightness and even structure changed as time went on. No one seemed to understand the issue, with the most likely concept being that it could be an asteroid that collided with something that exposed an icy body. Which could then be melting away. However, no one knows why or really how this asteroid managed to become a comet. This is one of those space anomalies astronomers seemed to differ heavily on.