Electro debuted in Amazing Spider-Man #9. His electrical powers make him distinct among the other members of Spidey's rogues.
At the time this episode was aired, Electro had only a handful of appearances: the aforementioned Amazing #9, Amazing Spider-Man Annual #1 when he joined the original Sinister Six, Fantastic Four Annual #3, and Daredevil Annual #1.
Being a member of the Sinister Six probably contributed to his inclusion in the series. However membership does not always have its privileges as this did not help Kraven.
A sudden thunderstorm blankets New York City at night. While on patrol, Spider-Man notices a bolt of lightning coming out of a window – at J. Jonah Jameson's house. Confused, he decides to investigate.
When he arrives at the window, Spider-Man finds a man in a green and yellow costume deactivating his alarm system – by generating lightning bolts from his hands. For some reason, he enters the small room through the window. Once inside he takes a picture of the lightning bolt man breaking into Jonah's hidden safe. [I guess that his camera didn't have a zoom feature which would have enabled him to take a clear picture outside. Away from the crazy lightning bolt man.]
This greatly angers the crazy lightning bolt man and he turns his electrical power against Spider-Man, claiming that his powers are useless against him, the master of electricity.
[At this point the title card appears. We are to infer that the villain's name is 'Electro'.]
Electro then unleashes a barrage of lightning bolts, forcing Spider-Man to hide behind Jameson's desk. While Electro grabs the contents of his safe, Spidey reconnects the alarm system with his webbing. While Electro is momentarily distracted, Spidey covers the window with his webbing. Electro easily burns through it and makes his escape by gliding along nearby power lines [This is really cool if you play Metallica's "Ride The Lightning" in your head as he slides along.]
The next day Spider-Man is charged with the robbery. Peter tries to prove to Jonah that "Electro" was responsible by showing him the picture; Jonah ignores it, thinking it's a fake. Betty tries to cheer Peter up by stating her belief that Spider-Man is innocent. Peter then sets out to clear his alter ego.
That night Spider-Man finds Electro atop a large electrical sign. His efforts to capture him fail, but he does manage to attach a spider-tracer to Electro. Instead of going in for the kill, Electro is content with leaving Spider-Man hanging on the ledge and sliding away [on a single, continuous electrical wire that stretches across what must be 20 blocks].
Electro soon discovers the tracer and sets a trap for Spider-Man. He robs a jewelry store, sets off the alarm, and leaves the tracer on the floor. Spider-Man discovers too late that he's been tricked and has to confront the police. He spins his web into a large sheet to cover his escape. The police open fire [and learn his webbing is bulletproof for some reason] but Spider-Man escapes.
Peter returns home to make up a new batch of webbing to help him defeat Electro. He also creates a device that will pick up electrical output in the amounts that he would generate. After a few false starts, his new device leads him to an abandoned amusement park.
Spider-Man quickly finds his adversary reviewing his latest acquisitions and announces his presence. When Electro unleashes more lightning bolts, Spider-Man creates a web shield that deflects them. He admits that he added asbestos to his web formula, which explains the electrical resistance. Electro becomes enraged and doubles his efforts to burn through his webbing. This only ignites a box of fireworks [conspicuously added here], which is used to cover his escape. Electro then leads Spider-Man on a chase through the park. He lures him onto the roller coaster track and tries to run him over with one of the cars, but fails [he can generate electricity and he tries to run him over??]. Electro then hides in a funhouse. Despite his tactical advantage, Electro is captured by Spider-Man.
To prove his innocence to Jonah, Spidey brings the webbed-up Electro to the Daily Bugle and leaves him outside Jonah's office complete with explanatory note. Jonah eats a large slice of humble pie as he tells Betty to call the police to pick up Electro. He then takes Peter's picture of the robbery and prepares to use it in an upcoming story exculpating Spider-Man.
One of the obvious things they cut out of this episode was Electro's origin. I will be the first to admit that you can't show someone getting hit by a bolt of lightning and surviving without giving kids some very bad ideas. Then again, you show Electro hopping on the power lines and riding off toward the background with no problem, so how exactly do you define what is and is not a repeatable act?
The vast majority of the episode was a streamlined story showing Electro doing what he does best: using his electrical powers to commit petty larceny and annoy Spider-Man until he is defeated by science. This usually takes the form of water, so I'll accept asbestos-flavored webbing as the deus-ex-mechina in this case. And believe it or not asbestos is resistant to electricity and was used in electrical insulation at one point. I initially thought this was contrived, but it is based in fact.
3.5 webs. Despite a few very silly points, this was one of the better episodes. The transitions between the Spidey/Electro fights and Peter/Betty/Jonah scenes are very smooth. They tell a good story and do so by effectively using the stock animation.
Electro does give Spider-Man a difficult time throughout the episode, going so far as to trick him with his own spider-tracer. Electro's depiction is over the top, but given that he's the villain, he's allowed to make statements like "My power is greater than yours!" It's a bit disappointing that he was captured so easily at the end.
Betty and Jonah do not act one-dimensionally as they do in other episodes. This may seem minor, but it helps balance the story. Jonah rejects Peter's "faked" picture because he thought it's a composite picture. The explanation is wrong but reasonable. When Electro is delivered to him, you can tell Jonah is annoyed that he has to exonerate Spider-Man, but he doesn't break down into a whiny outburst. This is a nice change. Betty is shown to be very supportive to Peter when Jonah accuses him of faking the picture of Electro and is level-headed when her boss asks for the previously rejected pictures.