Monkeyman! / Buses, Bikes and Subways - S5-E1
Trivia: The banana warehouse at the dock says "ROB RTSON" on top; Chris Robertson is one of the show's artists.
Trivia: In this episode, Sid is voiced by Taylor Gifaldi, the younger brother of Sam Gifaldi, Sid's original voice actor. Sid was recast because Sam Gifaldi went through puberty.

Timberly Loves Arnold / Eugene, Eugene! - S5-E22
Trivia: In "Timberly Loves Arnold", when Timberly shows Arnold her flower drawing, as Sid says, "Look, it's a flower named Arnold," part of his shirt is invisible in the first frame of the shot. This can only be spotted in slow motion or with pausing, therefore it's under trivia. (00:02:22)
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.