Neogenic Nightmare Chapter 1: The Insidious Six - S2-E1
Revealing mistake: When Rhino walks out of his cell, his left arm passes through the cell door.
Neogenic Nightmare Chapter 4: The Mutant Agenda - S2-E4
Revealing mistake: The same footage of Beast swinging through the trees while trying to catch up to Spider-Man is used twice. (00:08:20)
Neogenic Nightmare Chapter 5: Mutants Revenge - S2-E5
Revealing mistake: The same two guards are repeatedly shown trying to stop Wolverine and Spider-Man inside Landon's complex, despite the fact that Wolverine and Spider-Man are repeatedly shown dispatching them/knocking them out in other rooms within the complex. (00:05:20 - 00:08:15)
Neogenic Nightmare Chapter 5: Mutants Revenge - S2-E5
Revealing mistake: The same shot of two guards running towards Spider-Man and Wolverine is used three times. (00:05:20 - 00:08:10)
Neogenic Nightmare Chapter 5: Mutants Revenge - S2-E5
Revealing mistake: The shot of Hobgoblin tossing pumpkin bombs at the ceiling inside Landon's lab is a recycled shot from the previous episode when he tossed bombs at the ceiling inside the auditorium. (00:12:05)
Neogenic Nightmare Chapter 5: Mutants Revenge - S2-E5
Revealing mistake: The same shot of Beast looking dejected after Spider-Man calls him "blue boy" is used again a few minutes later when Wolverine is telling Spider-Man that he doesn't have to carry his burden by himself. (00:16:15 - 00:19:15)
Neogenic Nightmare Chapter 12: Ravages of Time - S2-E10
Revealing mistake: The shot of the Lizard whipping his tail at Silvermane and destroying a wall is recycled footage from the Lizard and Spider-Man's battle in the sewer from the first episode in the series.
Sins of the Fathers Chapter 1: Doctor Strange - S3-E1
Revealing mistake: When Mary Jane and the other servants of Baron Mordo are flying through the city, they literally disappear into thin air. Probably a problem with rendering the 2D animation within the 3D animation. (00:01:00)
Sins of the Fathers Chapter 1: Doctor Strange - S3-E1
Revealing mistake: The same shot of debris falling from the ceiling in Baron Mordo's lair is used twice. (00:14:25 - 00:15:45)
Sins of the Fathers Chapter 7: The Man Without Fear - S3-E7
Revealing mistake: During the fight with Kingpin recycled footage is used from Season 1 Episode 7 Doctor Octopus: Armed and Dangerous. It's obvious when you see the background looking like the warehouse along with Doc Ock's machine behind Spider-Man.
Sins of the Fathers Chapter 13: Goblin Wars - S3-E13
Revealing mistake: Several shots of the Green Goblin are recycled from the earlier episode "Enter the Green Goblin," with some of them being used multiple times in this episode.
Partners in Danger Chapter 8: The Return of the Green Goblin - S4-E8
Revealing mistake: When the Punisher is walking over to the couch to put Mary Jane down, he briefly glides across the floor.
The Wedding - S5-E1
Revealing mistake: After Scorpion causes the chandelier to fall onto Spider-Man, the camera pans to the right and Scorpion appears out of thin air onto the screen.
Secret Wars, Chapter 3: Doom - S5-E11
Revealing mistake: After Dr. Doom has stolen the Beyonder's powers, he demonstrates the powers to Ben Grimm in his throne room by teleporting Red Skull, Dr. Octopus and Smythe off the planet. Next he teleports all the heroes to his throne room, and the shot of all the heroes is from two episodes prior when all the heroes were battling the Lizard. This shot of the heroes also includes Ben Grimm in form as the Thing, meaning Ben Grimm was in two places at once. Spider-Man, the Lizard and the rest of the Fantastic 4 were also already prisoners in Doom's castle, which means they were all in two places at once as well.
Spider Wars, Chapter 2: Farewell Spider-Man - S5-E13
Revealing mistake: When Spider-Man is web-slinging with Stan Lee, they pass the same group of buildings twice, revealing it to be recycled animation.
Answer: I believe it was just a way to try and show the suit is "oily" or reflective. It also helps define the character's features since otherwise, he'd just be a flat black color. It's similar to how the black suit Spidey had blue outlines. (I don't know why they chose a pink/red color... maybe because red is associated with power/fire/war, so it's a more "evil" color?)
TedStixon