Some cats never stop some typical kitten behavior, such as kneading their mother’s tummy by moving the paws one by one around the nipple. This helps the little kitten to nurse, making suckling easier by creating a constant milk flow.
Some adult cats go back to performing these actions when they feel safe and comforted. Instead of their mother’s tummy they will happily use your sweater or blanket to knead and suckle on.
I have noticed this often – but not exclusively – in kittens that left their mothers quite early. Most cats seem to be in seventh heaven, really contented and often purring too whilst ‘kneading’. They look so happy that many cat owners probably think it’s well worth the wet patches on their clothes / pillow / blanket.
Occasionally a little claw may be used and that, of course, may slightly damage your clothing or Manchester. You could try to find your cat a super soft little blanket (or old sweater) that you can leave on your bed (or put on your lap) for this specific purpose.
If you’re going to look after someone else’s cats it worth asking beforehand if they have a favourite blanket or pillow. And don’t hesitate to pop that soft old sweater into your suitcase whenever you go on a pet sitting job…
Writing this I can’t but smile thinking back on one of the pets I grew up with; Bas, a Golden Retriever who enjoyed all the kneading and suckling that one of the cats performed on him. We often got strange looks when people noticed. But hey, it made for two happy pets and no damage!