Axolotl

SunKitten used to look after the school axolotl during the holidays (named 'Axl', predictably). It lurked in its tank and hardly moved until a worm was dangled in the water, and then it made for it like a starving crocodile. It was kind of cute.

Axolotls are actually really interesting because they don't metamorphose - they remain in (overgrown) larval form, but they do develop sexually. This sort of evolutionary alteration of the developmental process is called heterochrony.