Ok, this is going to sound odd ...
... but my cat has recently started to behave a bit oddly when I scratch the base of her tail. She sticks her tongue out and makes lapping motions and also purrs loudly - she clearly enjoys it, which is fine but why has she started doing this??
I'd not normally worry because the things cats do are often just weird but why this new behaviour? The lapping thing looks involuntary. I'll ask the vet next time I'm there (she's due her jags anyway) but anyone else come across this?