One of the most common experiences when geologists or archaeologists take new students out in the field is having one of them return with a rock and ask if it is a dinosaur egg, meteor, or arrowhead. There are countless random rocks lying around that resemble one of the above, so it's not unreasonable to make that sort of assumption. On top of that, everyone wants to find something cool like a meteorite or arrowhead.
The Old Man in the Mountain, one of the most famous mimetoliths. [Image source]
Those rocks are known as mimetoliths. Mimetos is Greek for imitator, and lithos is Greek for stone. They're a specific example of the phenomenon known as pareidolia, which occurs when the human brain seeks out patterns that don't exist in random data. One of the most common forms is seeing shapes in clouds.
The Rorsach inkblot test is one of the most practical uses we put this to. It's also used heavily in art- pareidolia is one of the main reasons our brains interpret optical illusions the way we do. Pareidolia is part of why we can assign so many emotions to simple line drawings in comics.
People aren't the only ones who experience pareidolia. Animals and computers do as well. Google Deep Dream is computer pareidolia in action. Cats thinking cucumbers are snakes is animal pareidolia in action. It seems to be an inherent quality to pattern recognition systems. When a pattern recognition system assigns either negative or positive value to a pattern, the system is more highly focused on finding that pattern in the world around them based on the absolute value assigned to said pattern.
Bibliography:
https://en.wikipedia.org/wiki/Pareidolia#Art