Crabby Author / Rich Kid - S3-E17
Trivia: The book publisher's name is "H. MacDonald"; Hugh MacDonald is a layout designer.
Sid's Revenge / Roller Coaster - S3-E8
Trivia: There are two versions of this episode. Originally, the closing credits appeared over the ending scene with Eugene going around and around in the roller coaster. When Nickelodeon switched to its "squeezed" credits format, a second version was created with the credits removed from that scene, and a new set of credits (over the "normal" credits background) added to the end. (This was later done with "Principal Simmons" as well.)
Answer: The show is based in present day times. Plus most cars aren't old fashtioned, I recall seeing a limo and not to mention a cherry picker, etc.