Among the interesting facts of the article "Pets" on Wiki:
In the series "The Secret of Ancient Treasures" Krosh and Yezik find the scheme of the simplest detector receiver of amplitude-modulated radio waves, but in the scheme of error - there is no diode, which should be installed in sequence with parallel connected condensator and headphones. The power sources of such a receiver are also not needed, and Yezhik has risked in vain, trying to include it in the socket.
This is just amazing >.<