Every so often someone finds a bunch of rats whose tails are knotted together. It’s called a rat king. (This one, with 32 rats, was found in a German miller’s fireplace in 1828.)
The rats are usually dead when they’re discovered, and no one has suggested a natural cause, so presumably humans are involved somehow.
Typically the rats are fully grown adults, so they’re not born this way, and their tails are often broken and callused, which means they’ve survived in this state for some time, fed by humans or by other rats.
Why would anyone do this? Who knows?