“Yale G.” was a man of unknown gender.
Behind the scenes
Yale G.'s name appears in the 2005 story Blueprint for Murder. Like all the names of authors in the story, it is an allusion to one of the Imagineers responsible for designing The Haunted Mansion in the real world — in this case, Yale Gracey, the special-effects whiz. Naturally, Yale Gracey was also plentifully homaged by his first name being transferred to Master Gracey and to Gracey Manor as a whole; it is purposefully ambiguous, in Jon Hastings's story, what the “G.” in Yale G. stands for, but it may not actually be “Gracey”.