A sea pen may look like an underwater quill, but it's actually a colony of individual polyps — one polyp becomes the stalk of the sea pen and the bulb that attaches it to the sea floor, while the rest form feathery branches. Some sea pens have only a few polyps, while others have as many as 35,000.

A silkworm wraps itself in a fluid substance from its silk glands that hardens to become a cocoon — this cocoon can be unravelled to a single strand reaching lengths of 1.5 km (1 mile). Inside, it "digests" its own larval body (called histolysis) before building up the body of a silkworm moth.

The coconut octopus carries seashells or coconut shells beneath its arms as it travels — using a few of its arms to hold the shells and the others to walk awkwardly along the sea floor. If this octopus encounters danger, it assembles the shells around itself, forming a kind of armour.

The common cockchafer spends its first 3 to 5 years below ground, growing as a larva. Then, all at once, these beetles emerge as adults in great numbers during spring. They clumsily buzz about, using their frilly antennae to find mates and reproduce — they live for only 6 weeks in this form.