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Seriously though, you can take them up to 3 or 4 times without a special waiver. After that, you have to explain to someone why you aren't enrolling in medical school after taking the test so many times.
You can take them 3 times without asking for any special permission to take them again. Everytime after that you need to get special permission to take the MCAT. I'm not sure who you have to get it from (probably AAMC).