Red and green spotted mushroom

From Discworld MUD Wiki

A red and green spotted mushroom is something you can gather in Uberwald forest in the autumn and buy from Jack Straw in Sto Lat.

It looks like this:

This is a very strange looking mushroom.  Not only is it excitingly coloured, it is shaped vaguely like a cross between a frog and a llama.
It looks nice and fresh.

When eaten, it causes you to hallucinate in the same way that gazing into a zodiac charm does.