A clip from the Children's Television Workshop pilot from 1969 has surfaced featuring Bob McGrath, Loretta Long and an unknown actor in the role of Gordon.
When the children's series finally went to air, Gordon was played by Matt Robinson. Hal Miller replaced Robinson in season three and Roscoe Orman has held the role since season six.
However, producers have been unable to identify the original Gordon pilot actor and have requested help from anyone who can shed light on his identity.
"We don't know who he is, and we'd like to figure it out. We've tried everything short of asking the internet, and come up empty. So we're asking you for help," reads a message on the official Sesame Street site.
"Email us with anything - anything - you know which could help us figure it out. Drop us a note a email@example.com and we'll start investigating.
"It could be something seemingly small; something like, 'My great aunt once said that her third cousin was almost on Sesame Street', or, 'There was a person in my neighborhood who said he was on Sesame Street in the late 1960s'. And as we learn more, we'll post it here."