One of the most well documented oddpets on this site, the Mushiking is a very detailed and very fun little pet. Raise your beetle, feed it a variety of items, equip it with stat boosters, and fight in a tournament!

The shape of the shell determines what type of beetle you can get. Stag Beetles (family Lucanidae) come from the most common pincer-style shell, Rhinocerus beetles (subfamily Dynastinae) come from the shorter horned style shell shown under the Stag shell on the left, Atlas beetles (genus Chalcosoma) come from the three-pronged shell.

The two-pronged shell where the pincers are shaped differently have the same roster as the Stag shell, with the addition of the Hirata Stag beetle.
The translucent blue shell with the yellow X is a special anime shell, but has the same roster as the normal Rhino shell.

Detailed fan-made instructions here.

This is the joy of having an ant farm without having any actual ants!

It's fairly hard to maintain and needs frequent attention to help ward off predators.

A fairly new pet that you can actually pet!

Despite being so new, there's not a lot of information in English about this pet.