What is the definition of Prepaid Blood Cells?

Prepaid blood cells: Think of these as the insurance policy for your circulatory system. They're like prepaid health plans, ready to jump in and save the day (or at least the hospital bill) when your body needs a little extra TLC. You know, the kind where you sign up for an annual membership and get a free coffee for life... minus the coffee, of course.

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Here's an edgy example sentence: "The prepaid blood cells decided to skip the annual membership renewal because they'd heard the insurance company was about to fire them for 'unnecessary medical expenses'."