Sometime over the long weekend or more probably on Monday itself, I thought I heard reference to Callum Brown being the sixth player to debut in the Melb v C'wood June holiday match.
After a study of the details on AFL Tables for Melb v Cwood matches played on those mid-June dates over the years
I think there are 11 names which should be recorded in that list:
1950 Arthur Pound (Melb)
1975 Terry Cahill (C wood)
1977 Brian Cook (Melb)
1983 Brett Cooper (C wood)
1993 Scott Simister (Melb)
2007 Danny Stanley (C wood)
2009 Jack Watts (Melb)
2011 Alex Fasolo (C wood)
2013 Adam Oxley (C wood)
2016 Tom Phillips (C wood)
2017 Callum Brown (C wood)
p.s. Yes, that Brian Cook - the Geelong CEO
Missing Tony Kelly (Co, 1983).
Not sure when the King's Birthday first became the Queen's Birthday (this site https://www.timeanddate.com/holidays/australia/queens-birthday suggests 1955), or whether it was always observed on the second Monday in June.