Its inhabitants built customised planets to order. These were fabulously expensive, so during the great galactic stock market crash they went into hibernation.

Magrathea was slowly forgotten, and many believed the stories about the people who made planets were mere legend.

The inhabitants of Magrathea were woken by a special order from some pan-dimensional beings, whose first custom-made planet had been destroyed.

Shortly afterwards, Zaphod Beeblebrox arrived on the planet in search of fabulous wealth and some answers to some questions he didn't know he wanted to ask.

This resulted in a large new crater being formed on Magrathea's otherwise unexciting surface due to the sudden impact of a large Sperm Whale.