Every other salamander grows up. Climbs out of the water, loses the gills, gets a job. The axolotl was invited to do this and declined — it keeps the frills, keeps the tail fin, stays in the water, and remains permanently, deliberately, the version of itself it actually likes.

This is not a defect. This is a whole animal that looked at the adult stage and said no thank you.

It also regrows limbs. Bone, nerve, muscle, all correctly arranged, no scar. Also spinal cord. Also heart. Also brain. The one creature on this planet that can take a real loss and simply grow the part back is the same one that refused to grow up, and if you think those two facts are unrelated, that's between you and the axolotl.

The Aztecs named it for Xolotl, the god who fled into the water and hid in this shape rather than face what was waiting for him. Worked, apparently.

Still smiling. Still nine inches long. Still down there.