- "Isn't that what family does?"
- —Uncle Monty to Violet when she asks him why he's caring for her, Klaus and Sunny
Dr. Montgomery was a brilliant herpetologist who discovered the Incredibly Deadly Viper, which was completely harmless, but he named it that to play a prank on his associates at the Herpetological Society. Upon first meeting the Baudelaires, he gave them homemade coconut cake. The Baudelaires quickly became fond of him. Montgomery preferred to be called Uncle Monty by the orphans. He mentioned how he had planned to take them to Peru with his assistant, Gustav and that Gustav had mysteriously "resigned" the day before the trip (he was actually drowned in the Swarthy Swap by Count Olaf). Montgomery unintentionally hired Count Olaf, disguised as a lab assistant named Stephano, as Gustav's replacement.
The children also watched a film called Zombies in the Snow while in the care of Dr. Montgomery, directed by Dr. Gustav Sebald. The movie, written in Sebald Code, warned them about an impostor (Stephano), but since neither the Baudelaires nor Dr. Montgomery had ever learned Sebald Code, they did not realize this. The Baudelaire orphans were aware that Stephano was Olaf in disguise, but they were unable to convince Montgomery.
Montgomery does, however, notice that Stephano is not a very good herpetologist, and believes he is a spy from the Herpetological Society. He rips up Stephano's ticket to Peru, and is later murdered by Olaf (who uses snake venom to divert suspicion, making it seem as if Montgomery died from an accidental snakebite). The Baudelaires expose Stephano's true identity, but Olaf escapes again.
Lemony Snicket: The Unauthorized Autobiography reveals that many of Monty's reptiles were trained to communicate coded messages. A ripped page from the book "The Mamba du Mal: A Snake That Will Never Kill Me"(written by Monty under an anagram pen-name), describes some phrases used by the Mamba du Mal. The Unauthorized Autobiography also contains a partial transcript of a V.F.D. meeting in which two attendees named 'M' appear. It is possible that Monty is one of these individuals.
Both the villains and volunteers want possession of Montgomery's collection of reptiles and amphibians. After Dr. Montgomery's death, a man named Bruce retrieves the animals for use by the Herpetological Society. It is stated in The Slippery Slope that Count Olaf later tricked Bruce into letting him take possession of the animals. This is the last mention of them in the books.
At the close of Who Could That Be at This Hour?, Hector briefly mentions Monty.
Montgomery was described as a "short, chubby man with a round red face." He was, being a Volunteer, a noble and kindly man. The Baudelaire's experience at his house, as strongly hinted, was probably the most pleasant throughout the series, as he became the closest thing of a new family to them. He had a lifelong interest of snakes and reptiles, having a large collection of them in his house.
- In the film adaptation Lemony Snicket's A Series of Unfortunate Events, Monty was portrayed by Billy Connolly.
- In the video game, he was voiced by Jay Gordon.
- In the Netflix series, Monty is portrayed by Aasif Mandvi.
- Mysteriously, in the book, Uncle Monty reveals he never had children or a wife, because he had no time for it and was leaving the idea for later. Already in the film, he said that had he a wife and children, but they died in a fire.
- In the book, Montgomery has red hair, in the movie he has gray hair, and in the video game he has black hair.
- It is possible that the name "Montgomery Montgomery" is a reference to Monty Python, a British comedy group. "Montgomery" may refer to "Monty", and the doctor's being an herpetological scientist that specializes in snakes may refer to "Python".
- It is also possible that the dual name, "Montgomery Montgomery" relates to Vladimir Nabokov's seminal novel, Lolita, in which the title character's name was Humbert Humbert.
- It is possible that the name "Uncle Monty" is a reference to the 1987 British cult film Withnail and I, in which there is a character named Uncle Monty, also portrayed as a fat, short man with a round, red chubby face.
- In the Netflix TV series, Montgomery Montgomery's mustache resembles that of Clash Royale's Electro Wizard.
- Who Could That Be at This Hour? (First mentioned)
- The Reptile Room (First appearance)
- The Wide Window (Mentioned only)
- The Miserable Mill (Mentioned only)
- The Slippery Slope (Mentioned only)
- The End (Mentioned only)
- The Beatrice Letters (Mentioned only)
- Lemony Snicket's A Series of Unfortunate Events
- Lemony Snicket's A Series of Unfortunate Events (video game)
- A Series of Unfortunate Events (TV series)