Roly polies, also called pill bugs or isopods, curl into a ball through a defence behaviour called conglobation. When threatened by a predator or disturbed, they tuck their legs inward and roll their segmented body into a tight sphere, exposing only their hard armoured outer shell. This protects their soft underside and vital organs. It is one of the reasons the roly poly has captured so much internet affection since the curling behaviour is irresistibly cute and endlessly shareable on social media.

Despite being called bugs, roly polies are not insects at all. They are crustaceans, placing them in the same group as crabs, lobsters and shrimp. Specifically they are terrestrial isopods in the order Isopoda. They breathe through gill-like structures called pleopods, which is why they prefer damp environments. This is what makes the isopod so fascinating to scientists and hobbyists alike. They are essentially a land dwelling crustacean that has successfully adapted to life out of water over millions of years.

The backyard roly poly (Armadillidium vulgare) and the giant isopod (Bathynomus giganteus) are both isopod crustaceans but they live in very different worlds. Roly polies are small terrestrial isopods, typically 1 to 2 cm, found in gardens and under rocks worldwide. Giant isopods are deep sea creatures living at depths of 170 to 2,140 metres in the Atlantic, Pacific and Indian Oceans and can grow up to 50 cm in length. Giant isopods went massively viral online due to their alien like appearance and their ability to survive without food for years, which further fuelled worldwide interest in the deep sea isopod plush trend.

Isopods have exploded in popularity as exotic pets over the past few years, largely driven by hobbyist communities on Reddit (r/isopods), YouTube and TikTok. They are low maintenance, fascinating to observe and play a vital role as decomposers in bioactive terrariums, which are themselves a trending hobby. Rare colour morphs of isopods such as albino, orange or purple varieties now sell for significant prices among collectors. The combination of internet virality, terrarium culture and their genuinely quirky charm has made isopods one of the fastest growing pet trends globally.

One of the most famous giant isopod viral moments came from Toba Aquarium in Japan, where a giant isopod named No. 1 famously refused to eat for over five years, surviving from January 2009 to February 2014 without a single meal before passing away. This story captivated the internet as a remarkable example of deep sea adaptation. Giant isopods in the wild are scavengers, feeding on dead whales, fish and squid that sink to the ocean floor. Their ability to gorge and then fast for extended periods is an evolutionary response to the scarcity of food in deep sea environments. This story significantly boosted worldwide interest in giant isopod plush toys and collectibles.