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)
Continuity mistake: When Frank Castle walks up to Murdock, the chains are wrapped around his torso, two over his chest and three over his abdomen, but when the shot cuts, it's one over his chest and four over his abdomen. (00:17:40)
Continuity mistake: When the Punisher knocks out Daredevil he wakes up with a gun taped to his right hand. When the Punisher says that Daredevil has to shoot him, Dardevil struggles to escape from his chains and we get a shot from his right side, where the gun is no longer there. In a later scene it returns. (00:32:05 - 00:34:55)
Character mistake: When Matt is talking to his priest Father Lantom, he says "it was a nice sermon" instead of "it was a nice homily." In the Catholic church "homily" is the correct word; sermons are Protestant. (00:11:30)
Continuity mistake: The bruises on Castle's face are dark then faded and then dark again.
Continuity mistake: While Matt and Karen are talking outside of the courthouse, the sun changes between shots.
Seven Minutes in Heaven - S2-E9
Continuity mistake: After Frank stabs Dutton in his jail cell and Dutton falls to the floor, Frank's white prison uniform is clean, but when Frank exits the jail cell there is blood on the collar of his uniform. (00:40:05)
Seven Minutes in Heaven - S2-E9
Continuity mistake: The wound on Fisk's right cheek changes length and position during the whole chapter.
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)
The Dark at the End of the Tunnel - S2-E12
Visible crew/equipment: When Frank closes the door to the shed, you can see a crew member in the trees to the right swaying left to right as if he were looking for something. (00:45:15)
A Cold Day in Hell's Kitchen - S2-E13
Continuity mistake: Before the last fight there are over 30 ninjas waiting for Daredevil and Elektra. Elektra kills like 5 or 6 of them and Matt struggles just with Nobu, but when the fight is over the rest of the ninjas are dead below the water tank.
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.
Blindsided - S3-E4
Continuity mistake: As Marcy says "the more public, the more you're protected", her hands are flat on Foggy's chest. Cut to a shot from the side and her hands are clasped in front of her by his stomach.
Continuity mistake: When Blake Tower is talking with Foggy in his car, when Tower says "You need help, Nelson", there are raindrops along the interior of the driver side door. The shot cuts to Foggy, and when it cuts back to Tower, the raindrops are suddenly more faded. (00:14:00)
Continuity mistake: When Matt and Foggy are talking with Nadeem after he testifies, in some shots, Matt is holding onto the top of his cane, but in other shots, his hand is further down. (00:39:35)
Visible crew/equipment: A random hand appears on the left side of the screen when Matt is punching Fisk. (00:33:59)
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.