Mythbusters "Cannibal Mouse" (lost unaired segment of television series; 2006)
Mythbusters is a popular science entertainment TV program that enacts/puts to the test many myths and urban legends, determining whether it is "plausible" or "busted".
In the 2006 episode of Mythbusters Episode 55 "Steam Cannon", one myth that was tested was the saying "there's more nutrition in the cardboard box than the cereal."
In a Q&A, host Adam Savage informed that there was an experiment that never made it to air.
According to Adam, they had 3 lab mice in three experiment groups; one group is eating normal mice food, one group eating the sugary cereal, and one group eating cardboard box pellets. Jamie noticed that the cardboard group were acting strangely. When they came in, they found that one of the "cardboard mice" ate the other two mice, to which Adam made jokes about.
Due to the disturbing material, Discovery refused to let this be part of the episode. In the interview, Adam admits to making a rough cut and showing it at "Northern Michigan Tech" (likely referring to either "Northern Michigan University" or "Michigan Tech University"). When Discovery found out, they told Adam never to show it again.
Due to it being graphic animal violence, it is very unlikely it would ever resurface, considering Mythbusters tries its best to keep a family-friendly image and not show any harm happen to living beings (not testing the myth of "drying a dog in a microwave" in any form, for instance).