The Return of Hydro-Man: Part 1 - S5-E7
Stupidity: When Spider-Man is working in the lab, he uses his webbing to barricade the door shut so no-one interrupts him. When Debra Whitman shows up and asks who is in there, he identifies himself as Peter Parker. When he is finished with his work, he leaves out of the window so that by the time the security guards break the door down, he has vanished. Since he used his webbing to keep the door closed, it would be pretty easy for Debra and the security guards to figure out that Peter is Spider-Man since Spider-Man's webbing is at the scene and Peter seemingly vanished into thin air.
Answer: Yes. Many things that would have been in the sixth season would have had Norman Osborne returning from limbo and reclaiming the title of the Green Goblin, Richard Fisk, the son of "The Kingpin" Wilson Fisk would return as a crime lord known as "The Rose", Ghost Rider would have appeared to help Spider-Man stop Dormammu from returning to Earth and Madame Web and Spider-Man would rescue Mary Jane from limbo.