Parker learns that the mail Drone the cloud accidentally destroyed has come back for revenge. Parker, Lily, and Mayor Peeve team up to stop the zombie mail Drone once and for all.
"I Know What You Did Last Mail Off" provides examples of:
- Animation Bump / Art Shift: When Parker turns into a Super Saiyan, the animation becomes smoothier as it goes for an Animesque look. This sequence was animated by Regis Camargo.
- Continuity Nod: Being a sequel episode to POSTBOT 3000, but also the episode consist of a lot of recurring one off characters.
- Dance-Off: This was done in order to get rid of the drone.
- Enemy Mine: Although Mayor Peeve hates the Middlemost Post for blocking the sun from his town hall, he teams up with Parker to get rid of the drone.
- Freeze-Frame Bonus: It took 24 frames to build another new Post Bot.
- Hard-Work Montage: Parker and Lily building a huge robot in order to defeat the drone.
- Jaw Drop: As soon as the recap ended, Parker gets this when they remembered what they did with drone.
- Leaning on the Fourth Wall: The drone removing the backgrounds and outlines of the characters to the point where it's all a white void.
- Let Us Never Speak of This Again: The mayor doesn't want Parker to know what they did together to their co-workers, but then Parker ends up telling them the events anyway.
- Out of Focus: Angus and Russell in the second part due to being eaten by the drone. As a result, they only appear in the very end with no dialogue.
- Pop-Culture Pun Episode Title: The title references I Know What You Did Last Summer.
- Previously on…: It shows up as soon as Parker suddenly remembers the event of POSTBOT 3000.
- Roaring Rampage of Revenge: The Drone Parker spent the entire episode making a rampage at the mountain as revenge for being destroyed by Parker.
- Sequel Episode: To POSTBOT 3000.
- Shout-Out: Parker goes Super Saiyan. And one of the robots Parker and Lily built to defeat the drone resemble a Transformer.
- Tempting Fate: Angus reassures that he's still here and there's nothing to worry about, but then the drone came out and eats him.
- To Be Continued: Part 1 ends with the narrator asking a serious of questions.
