"Ashes to ashes, and dust to dust, Snoopy will find it, and find it, he must."
— Linus van Pelt
What happens when you combine a Christmas Episode with a kid-friendly Whodunnit? You get this animated Peanuts especial that aired in 1974.
It's winter, so Woodstock builds a nest and struggles with a stubborn straw while Sally gets frustrated about what has to be the nth science project her teacher has assigned. The next day, the nest has disappeared and Snoopy has to become a Sherlock Homage to help his friend.
Preceded by A Charlie Brown Thanksgiving and followed by It's the Easter Beagle, Charlie Brown.
It's a Mystery, Charlie Brown contains examples of:
- All for Nothing: Woodstock "legally" gets his nest back after all the time spent searching for it, but upon resting in it during The Stinger, the nest gives way and falls to pieces.
- Artistic License – Law: Lucy acts as the judge of a civil case over Woodstock's nest, while Snoopy acts as Woodstock's defense attorney representing him, despite neither Lucy nor Snoopy having any legal jurisdiction to do so.
- Behavioral Conditioning: After losing the court case involving Woodstock's nest, Sally, with some help from Snoopy, does a replacement science project about Pavlov's experiments.
- Bubble Pipe: To complete his Sherlock Holmes attire, Snoopy produces a pipe out of nowhere and starts "smoking" it, which is indicated by the bluish bubbles being released. It's complete with a Running Gag of a huge bubble traversing the town.
- Cowboys and Indians: Peppermint Patty mistakenly thinks that Snoopy is playing Cops and Robbers, and chases him all over her house wearing a Domino Mask.
- A Day in the Limelight: The special is mainly focused on Woodstock. Its introductory scene is him building his winter nest and the rest of the plot revolves around how his nest goes missing and who steals it. Normally, Woodstock is a minor character.
- I Just Want to Have Friends: When arriving at Pig-Pen's house, he's elated to have any people over, only for Snoopy and Woodstock to run off because of his congesting dirt, with Pig-Pen yelling to them that he tends to not get many visitors in the first place.
- Judicial Wig: Lucy dons one of these when she decides to play the "judge" to solve the dispute between Woodstock and Sally.
- Mean Character, Nice Actor: When Peppermint Patty thinks that Snoopy is playing Cops and Robbers, she gladly takes on the role of the villainous robber, Domino Mask and all.Peppermint Patty: Yer money or yer life, ya' dirty rat!
- Penultimate Outburst: Lucy uses it word-for-word at the end of a "trial" where she decides that Woodstock can have his nest back from Sally.
- Private Detective: While he doesn't get paid, Snoopy definitely doesn't work for the police force. He's on the case of who stole Woodstock's nest. After falsely accusing Lucy and being forced into play-acting with Peppermint Patty, Snoopy and Woodstock find the nest at school where Charlie Brown's sister Sally appropriated it for a science project.
- Sherlock Homage: Snoopy dons a deerstalker hat and Meerschaum bubble pipe to play detective in order to find Woodstock's missing nest.
- Stealth Insult: Sally thinks that Woodstock's nest is a prehistoric bird's nest, under the logic that it looks so ugly that it has to be prehistoric.
- Surprisingly Happy Ending: For Sally. After having Woodstock's nest taken away from her and losing it in a mock court hearing, she's left without a science project. However, Charlie Brown decides to make it up to her by having Snoopy recreate the behavioral experiment with Ivan Pavlov's dog, which earns her an A.
