Well in my opinion, the first dozen of season four episodes have that same classic feeling to me. Like 1-3. I mean Fear of a Krabby Patty, The Lost Mattress, Skill Crane, Selling out, Mermaidman and BarnacleBoy 6: The motion picture and Where's Gary are all very funny. While there are other good Season 5 episodes, Night Light, Friend or Foe, Sing a song of Patrick, New digs, Krabs a la Mode etc.. , they still don't have that classic feeling. so I say season 4.