From the Super Mario Wiki
A Dark Mechawful.5 (known as Dark Mechawful 1.5 in PAL regions) is an enemy found in Mario & Luigi: Bowser's Inside Story. When Bowser destroys a Dark Mechawful and leaves the ejecting head alone for a turn, the head becomes a Dark Mechawful.5, gaining a new metal body. The differences between the two are:
When Dark Mechawful.5 attacks, the numbers on its chest sometimes malfunction, making it tricky for Bowser to counter.
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