The main four play spies. Mr. Cat decides to be on the good guys' side, so the role of the villain is given to Quack Quack; Stumpy, who wanted the villain role but is stuck being a good guy, betrays his team.
"Let's Play Spies" contains the following tropes:
- Afraid of Needles: Stumpy is afraid of needles, and faints when Mr. Cat shows him one.
- Arson, Murder, and Jaywalking: See Mood Whiplash below.
- Beard of Evil: Parodied. Kaeloo gives Quack Quack (who is playing the villain) a fake beard to make himself look evil, and when Stumpy reveals that he is a traitor, he puts on a fake beard as well.
- Bear Hug: Bad Kaeloo gives one to Stumpy, Quack Quack and Mr. Cat to show how much she loves them. Their heads explode.Bad Kaeloo: Oops, friends broken.
- Brief Accent Imitation: Kaeloo tries doing a British accent for a few lines. Key word, tries.
- Does Not Know Her Own Strength: Bad Kaeloo gives a Bear Hug to Stumpy, Quack Quack and Mr. Cat. Their heads explode because she squeezed them too hard.
- Fainting: Stumpy's reaction to seeing a needle.
- I Miss Mom: Mr. Cat, who left home prior to the series, says that he misses his mom after being shot with the Truth Serum.
- Immediate Self-Contradiction: In the French dub, Stumpy says he is not afraid of needles and then passes out as soon as he sees one. Averted in the English dub where he admits that he is.
- Mood Whiplash: After getting hit with the Truth Serum, Bad Kaeloo admits to feeling inferior and less loved than regular Kaeloo, Mr. Cat talks about the abuse he received at home and his horrible body image, and Stumpy confesses that... he enjoys wearing girl clothes and makeup when nobody is looking.
- Muscle Angst: One of the things Mr. Cat says after being hit with truth serum is that he wishes he had bigger muscles.
- Nigh-Invulnerable: Quack Quack is fine despite being visibly injured alongside Stumpy and Mr. Cat. Stumpy and Mr. Cat need him to push them around on a hospital gurney since they haven't recovered enough to get back on their feet.
- Only in It for the Money: Mr. Cat assures Kaeloo that he wouldn't have betrayed her if not for the fact that he badly needed the money.
- Sdrawkcab Name: The main four's code names are their own names backwards: Kaeloo is Ooleak, Stumpy is Ypmuts, Quack Quack is Kcauq Kcauq and Mr. Cat is Tac Retsim.
- Still Sucks Thumb: Under the effects of the Truth Serum, Mr. Cat starts sucking his thumb while crying about how much he misses his mom.
- Truth Serum: Mr. Cat attempts to inject Kaeloo with one. Due to her suddenly transforming, the serum is also flung at the others, and everyone winds up with a dose.
