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Ackpows are sphinx-hat wearing servants working for Mimi in Super Paper Mario. They are featured in Chapter 2-3 inside Merlee's Mansion. Ackpows' roles are to make sure all of the other servants are working and pay them with Rubees after they're done. Also inside the mansion, Mario and Princess Peach can find a ? Block containing a Mushroom that requires a payment to the nearby Ackpow upon use.
According to Tippi, they act like they are all important, but in reality, they are in debt to Mimi just like every other servant. This is very similar to the system of work the Egyptians used. Their style of dress also seems to reference the Egyptians as well. After Mimi is defeated, the Ackpows are released from servitude.