A good ^{[Needs evidence]} street doc, he puts the pain in healing.

Shrek and him know each other from way back.
His family and Shrek's family were close, their parents that is. Back when they were kids, Painboy and Shrek just met up with each other when the parents hung out together.
Nowadays other than medical treatment requests, they keep in contact through seasonal greetings, like New Years and the jolly winter season's OrkMas.