A cat has a very adaptable tongue. When it drinks the edges of its tongue curl, making its tongue into something like a long spoon. A cat's tongue is a very useful tool for cleaning itself. If a cat licks your hand, you will notice that its tongue feels a little rough. This is because all cats' tongues have comb-like spikes that are called papillae.
Cats use their tongues to clean their fur, as well as for scraping meat from bones.
Cats have extremely sensitive whiskers, which are, in fact, feelers. A touch on the feelers sends a message to the cat's brain that in turn lets a cat know by experience whether or not it will fit through the opening. Usually, if the whiskers are free and clear, it is a good bet that the rest of the cat's body will be too. Unless, of course, you have a very fat cat. Read through this passage about cats.