Continuity mistake: When the paramedic examines Foggy he places the stethoscope around his neck with the chest piece hanging to his left, but when it cuts to the view from inside the ambulance the stethoscope's suddenly hanging around his neck the opposite way. (00:17:30)
Other mistake: When Matt and Claire are on the roof and Matt says "A dead guy, a guy I witnessed burn to death," Charlie Cox's natural English accent slips through. (00:41:35)
Chosen answer: After some research, I can say that no, Cass is not a character of Marvel, nor is he present in the Netflix show. As far as I can tell, it's either a real person, or a random name chosen for the coffin, most likely the former. In another season of Daredevil, the show utilized a real cemetery displaying real names in the tombstones.