M. McGonagall

M. G. McGonagall was a Gryffindor student at Hogwarts School of Witchcraft and Wizardry in the early 1970s. They played on the Gryffindor Quidditch team, winning an award for it in 1971, which was displayed at Hogwarts on a plaque that also bore the names of James Potter and R. J. H. King.

This person may have been related to Transfiguration teacher Minerva McGonagall.

Behind the scenes

The name M. G. McGonagall appears only in the film adaptation of Harry Potter and the Philosopher's Stone. M. G. McGonagall cannot have been the same person as Minerva McGonagall, as Minerva attended Hogwarts as a student circa 1937 to 1944, and taught there beginning in December 1956.
In the video game version of Harry Potter and the Order of the Phoenix, a trophy can be found in the Trophy Room near the Great Hall. Inspecting it causes Ron to comment on the presence of Minerva McGonagall's name near James Potter's, to which Harry speculates that it may have been due to her being Head of Gryffindor House at the time. However, these two awards cannot be considered the same, as the one seen in the film adaptation of Harry Potter and the Philosopher's Stone is a plaque, and not a cup.