I think it's to draw parallels for the various characters who can't understand how to cope with the horrible hand they've been dealt. Stone has terrible eczema and is whipped back and forth between doctors who all sell him cures that may be more harmful than the condition. The advice he receives from one doctor is…

On the eczema-hating: After this episode, I actually thought it was a pretty clever plot device to highlight the similarities of Stone and Naz (and Naz' family) thematically. I don't view it as a cartoonish or contrived trait at all. It didn't make sense to me until the support group scene, but I think it's use is…

Interesting exchange from an informed commentariat. Two thoughts to share, having just watched this episode last night:

A time traveler and purple man rabbit? So I assume he is Frank from Donnie Darko.