Scottish Water staff have also found a platoon of toy soldiers, a live frog and a goldfish clogging the pipes.
The firm spends £6m a year clearing system blockages and urged people to think about what they flush away.
Many items also enter the system by falling into drains or manholes found in fields and roads.
A worker at the Dunfermline waste water treatment works was stunned to see a Mexican desert kingsnake curled beneath a metal grid boardwalk he was strolling along.
He contacted the Scottish SPCA, who collected the non-venomous constrictor snake and took it away.
‘Credit card’
A live badger found in a pumping station well at Drongan in Ayrshire also made a full recovery after it was rescued by the SSPCA.
A goldfish named Pooh, recovered in East Kilbride, and a frog found in a pump in Dornoch, Highlands, were none the worse for their time inside the sewer system.
However, a sheep found in a manhole chamber and a cow recovered from a storm tank were not so lucky.
As well as animals, Scottish Water workers have recovered an eclectic collection of items, including an iron which worked, despite its time in the network.
Staff in Dumfries even found a credit card of one of their colleagues, which had been stolen from his wife’s handbag on a night out.
‘Endangers health’
The thief stole some money then flushed the contents of the bag down the toilet, and the credit card eventually reappeared at the sewage plant.
False teeth and mobile phones are often found, as are rings and watches, which are handed to police.
Scottish Water dealt with more than 36,500 choked drains last year and urged the public to help reduce the amount by being more careful.
It estimated that 340 million items of sanitary waste were flushed each year and said 55% of all sewer blockages are caused by people disposing of cooking fat down their sink.
Waste water general manager Rob Mustard said: “When sewers, pumping stations and sewage works get clogged they overflow and sewage escapes into rivers.
“This endangers public health, wildlife and the environment.”