The British SOE (Special Operations Executive) used many inventive and exotic ways to disguise their explosive devices during the Second World War. One of these was a dead rat developed in 1941.

The idea is that a SOE agent will procure hundreds of rats where they will be skinned, filled with plastic explosives, and sewn up. In theory, the rat bombs will be placed among coal beside a boiler located in a German factory, power station, or similar installations. The stoker who tends to the boiler would dispose of the unpleasant discovery by shoveling it into the furnace. The small amount of explosive in the dead rat, combined with the highly pressurized steam boiler, would cause an explosion, dealing great damage to the installation.

Despite its innovation, the first container of dead rats was intercepted by the Germans before it could be used. Still, the idea of rodents stuffed with explosives caused a psychological disruption among workers and military personnel as they had to pool resources and conduct extensive searches to mitigate the threat.

https://www.wikiwand.com/en/articles/Explosive_rat

https://www.theguardian.com/uk/1999/oct/27/richardnortontaylor

https://www.bbc.co.uk/history/worldwars/wwtwo/soe_gallery_05.shtml#:~:text=The%20idea%20for%20the%20’exploding,was%20shovelled%20into%20the%20fire.

https://www.amusingplanet.com/2020/09/the-failed-british-plan-to-destroy-nazi.html