Headmaster (Transformers) - Transformers: Armada

In the 2002/2003 toyline, Transformers: Armada the figure known as Overload was identified as a Headmaster, whose head was formed by the Mini-Con, Roll-Out. However, although Overload is featured briefly in the animated series, this aspect of the character was not touched upon. He did appear more prominently in the Dreamwave comic book series.

Similarly, the Armada toy Sideways featured two Mini-Cons, Rook and Crosswise which could each transform into heads (however, Sideways had a standard head, thus he was not a true Headmaster).