Is it a Maine Coon thing?
Tonight was jabs night...
Obie stalked out of his (dog sized) basket glared at the vet, had his jabs and then tried to stalk onto the vets counter and whack down the syringe... bad ass to the bone.
Ophie faked sleep in her basket.. was gently removed whereupon she flopped on her side and went completely limp. Had her jabs and lay there. Went to usher her back into her basket... nope.. completely floppy and when the vet, laughing, nudged her back end she concertina'd up in a floppy set of wrinkles! In the end he lifted her, where she lay over his hand like a jelly until back in her basket!
Morph used to do EXACTLY the same.. hence finding it funny not worrying. But I've never seen any other cats DO this!