Continuity mistake: When Karen is telling Mat and Foggy the story, and mentions that things got blurry like she was drugged, she is making gestures with her hand. Between shots, the position of her hand changes from one spot to another. (00:27:30)
Continuity mistake: When the debt collector is talking to the man in the park eating area, there is a cup on the table in front of them with a straw sticking up, but leaning to one side. Each time the camera cuts to a different angle and even coming back to the same angles, the straw is always changing positions pointing in different directions. (00:19:36)
Continuity mistake: Foggy meets Brett at a subway and begins talking. He says they have been enemies since they were four but not to blame it on career choices. Between shots, Foggy's hand goes from down at his side to suddenly on his own chest. (00:09:58)
Continuity mistake: Foggy is on the phone with Mat, telling him about some people and he wishes he was blind. There are other pedestrians walking behind him in this shot. When it cuts to a close up, the people behind him suddenly disappear.
Resurrection - S3-E1
Continuity mistake: When Matt is recovering in the orphanage, his bandages around his torso keep changing position. They go from just barely below his nipples, to covering them completely, to way below them in the same scene.
The Ones We Leave Behind - S1-E12
Character mistake: After Gao and two of her men walk by in the warehouse, Matt jumps down at attacks one of the guys. The other guy is behind with a sub machine gun in his hands. While he was walking it he carried it partly pointed down to the ground like normal. Once the other guy was jumped, he begins to fire, but the actor continues to point the gun down at the floor like this shooting the ground no where near anybody. He only starts to raise it once Matt get's close to look like he gets hit. (00:40:01)
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.