This made me smile. He sounds like he was great to have as a teacher.
I’ve had this experience in a couple of places. I recall the National Museum of Natural History had a diorama of a Cambrian sea that had Hallucigenia upside down and back to front. And in the St. Louis Zoo’s bird house I found a number of signs that were wrong; for example, they claimed that seriemas were related to cranes. Couple of knee-slappers, I know.
I do consider that a fun example. The story of Hallucigenia illustrates how scientists are constantly gathering new data while being always ready to revise their understanding. (Of course, this is opposite to what a lot of amateur critics claim about scientists being driven entirely by bias and maintaining some imagined status quo of interpretations of the data.)
As this article explains, only more recently have scientists figured out which end is the head and how to orient it up/down. The fact that scientists decided to call it Hallucigenia emphasizes that it looks like something one might imagine while in a dream-like state.
Here’s a fun animation of what a live Hallucigenia would have looked like. It’s also a great little video for explaining to non-scientists how scientific discovery depends on scrutinizing new data with a willingness to change one’s mind.