robot shit

Empty (spent) nitrous oxide canisters, 'whippits', or cream bulbs often discarded and left lying around on the ground at music festivals or technivals where this is a popular drug of choice. The term originated from the observation that they resemble the faeces of robots, being both metallic and the shape of a passed stool.

Wow those guys must have had a big night last night, there's robot shit all around their tent!