Homer hires a private investigator to learn more about Lisa, until the P.I. frames dad and daughter for a crime they didn't commit.

!! Tropes:

* BaitAndSwitch: The sign Bridge Out...standing
* ChekhovsGun: To compensate for the inability to get a security diary for her, Bart gets Lisa a laser pointer for her birthday. At the climax of the episode, Lisa uses it indirectly against Dexter Colt.
* ClearMyName: Homer and Lisa have to clear their names when a detective steals animals from a lab and frames them.
* CreditsGag: Bart steals Lisa's new diary, which shocks unauthorized users who try to open it, and tricks Homer into an attempt to read it as a bedtime story.
* HypocriticalHumor:
** Bart complains that Lisa makes him come off as a {{Jerk|Ass}}... while reading her diary.
** Homer is shocked that Dexter Cole, a man who will spy on her daughter for money, could be such so greedy.
* {{Irony}}: Invoked. Homer tries to make an ironic comment about Dexter Colt getting blinded by Lisa's laser pointer.
* MajorInjuryUnderreaction: Not a physical injury but Carl casually mentions he has severe schizophrenia.
* MegaMealChallenge: The P.I.'s bill includes 40 dollars for a steak. The detective explains that it'd be free if he managed to eat it all.
* NobodysThatDumb: When Lisa is framed for a crime she didn't commit and the cops sees her and Homer flees when they arrive to arrest her, Chief Wiggum said something that even his own son, [[TheDitz Ralph]], knew the answer to:
-->'''Chief Wiggum''': ''(to Marge)'' Would an innocent person flee?\\
'''Chief Wiggum''': No, really. Tell me. I honestly don't know.\\
'''Lou''': Chief, no.\\
'''Ralph''': Even ''I'' knew that.\\
'''Chief Wiggum''': Yeah, yeah, I'm not... I'm not good.
* NoodleIncident: Homer chopping up Bart's skateboard with an axe for the insurance money.
* RunningGag: Homer covering himself with shoe polish.
* ShoutOut: When Lisa dyes her hair with shoe polish, she comments that she looks just like [[WesternAnimation/ThePowerpuffGirls a Powerpuff Girl]]. [[http://simpsons.wikia.com/wiki/File:The_Dad_Who_Knew_Too_Little_81.JPG She even has Buttercup's hairline.]]
* SilverBullet: The P.I bought some because he assumed Lisa was a werewolf, it's not clear if it's just to pad the bill or he really did it.
* TakingTheBullet: Or more accurately taking the human cannonball.