Who is Sullivan's John?

[Shunpike]

I found a drawing of him in the Art section. Does anyone know who he is, because I don't recall ever seeing him in GKC. If he has appeared in the comic, could you link me to the page/s?

Thanks.

Edit: The drawing of him his here: www.gunnerkrigg.com/art/john.jpg

[Asuka]

Sullivan's John has appeared in the background of some panels (like when Basil was introducing himself to the class in chapter 2) and in the bonus page for chapter 5.