This isn't just the least-fun thought experiment, it's a medical malady common enough to have its own name. Learn how internal hirudiniasis works (and why you don't need to panic if if happens to you) in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/marine-life/swallow-leech.htm

How Did the Great Stink of London Work?
12:10

BrainStuff Classics: How Do Blue Whales Work?
08:41

Do Political TV Ads Really Change Minds?
12:26