Similar to crocodiles only dwelling on land, monitor lizards are the lizards most likely to be cast as antagonists in animal fiction. They are also common foes in jungle settings.
One reason why monitor lizards get such a bad rap is from their large size and strength, as well as their rather intimidating appearance, since they stand as the largest lizards in the world and are capable of taking down deer and water buffalo. Their habit of flicking out their tongues a lot (they "taste" the air to, well, monitor it), looks like a Maniac Tongue if the lizard is somewhat anthropomorphized.
What also doesn't help their reputation is their diet, as they're often seen as scavengers due to the amount of carrion they eat. In fact, for a long period of time it was assumed that this reason why they had such nasty bites, where the deadly bacteria they picked up from carrion were responsible for taking down prey. However, later studies conducted in the mid-to-late 2000s debunked this theory, with it instead being revealed that monitors are among the few lizard species with a venomous bite. The venom further adds to their villainous reputation, because Poison Is Evil.
In fiction, monitors will usually be a generic kind. If a real-life species does get chosen, it usually be the Komodo dragon; this is partially because Komodos are the largest kind of monitor and look rather intimidating, partially because they're the only species of monitor lizard known to (rarely) kill and eat humans, and partly because it's the only species audiences will be familiar with.
Komodo dragons are generally portrayed as powerful, dangerous Super Persistent Predators; fitting with their intimidating appearance and size. "Lesser" monitors, conversely, are often portrayed as sneaky, thieving slimeballs, with a particular taste for eggs. Obviously this adds to their negative portrayal, since eggs are effectively other animals' kids-to-be.
For series featuring prehistoric life, expect the prehistoric monitor lizard Varanus priscus a.k.a. Megalania, an extinct Australian species that was at least twice the size of the modern Komodo dragon (but in fiction tends to get exaggerated in size and ferocity to dinosaurian proportions). Another common examples are mosasaurs, which are not truly dinosaurs but rather large, aquatic monitor lizards that may fill a role as a Threatening Shark in prehistoric-set works.
Sub-Trope of Reptiles Are Abhorrent. For monitor lizards pretending to be dinosaurs, see Slurpasaur. Contrast Lovable Lizard, for more benign lizards— needless to say, monitor lizards are rarely used for that trope. See also Snakes Are Sinister and Never Smile at a Crocodile for other villainous reptiles.
- Aggretsuko: Tsubone (named Scatherine in the fan subs), an anthropomorphic Komodo dragon, is a mean-spirited, sometimes downright sadistic senior secretary who acts like a Mean Boss to the protagonist.
- Kaiju Girl Caramelise: When Manatsu brings Kuroe and Rairi to "Kaiju Island", the former two encounter Megalania-sized monitor lizards that gang up on and try to eat the girls, forcing Kuroe to turn into Harugon to save Manatsu. A Wham Shot at the end of the chapter shows several of the lizards with wings and horns like Harugon's, implying some genetic connection to Kuroe.
- Whether by accident or design, many reconstructions of theropod dinosaurs have varanid-like traits; in particular, featherless renditions of dromaeosaurs look like bipedal Komodos. Special mention should go to the first reconstruction of a Megalosaurus, as depicted at Crystal Palace in London◊, which looks like a cross between a monitor lizard and a wolf.
- The Cretaceous period monitor lizard palaeosaniwa is amongst the various prehistoric species rescued for the titular zoo in Prehistoric Park Reimagined. And while not evil per se, they do prove fairly intimidating to the park staff by virtue of their size and carnivorous disposition, and they are also perfectly capable of being rather aggressive when provoked sufficiently enough.
- In What Lies Beyond the Walls, every single monitor lizard mentioned in the story is murderous and/or cannibalistic. This is somewhat jarring, considering how gray all the other characters are and that the other vermin consistently deconstruct Always Chaotic Evil.
- Adventures in Zambezia: Budzo, the Big Bad is a vicious monitor lizard with a taste for birds' eggs who was responsible for killing the protagonist's mother.
- FernGully: The Last Rainforest features a blue and red monitor lizard that sings an entire musical number about wanting to eat one of the protagonists. However, when not hungry, he turns out to be a pretty nice guy.
- The Rescuers Down Under features Joanna, a goanna who serves as Percival McLeach's Right-Hand Attack Dog who has a massive appetite for eggs, including the eggs of the giant eagle Marahute.
- Curse of the Komodo is a Syfy Channel Original Movie involving Komodo dragons which have been enlarged to sauropod proportions by secret genetic experiments on a remote Pacific island, turning them into bulletproof monsters capable of keeping pace with a speeding car and venom that can turn people into zombies.
- Jurassic World: According to supplementary material, the raptors have monitor lizard DNA mixed in, presumably explaining their lack of feathers.
- King Kong (2005): While lost in the vast and deadly jungle of Skull Island, Ann is attacked by several huge lizards that are clearly supposed to be beefed-up komodos. These monitors are in turn devoured by a T. Rexpy, which hasn't had its fill yet and proceeds to chase after Ann too.
- Komodo is about a colony of Komodo dragons living on an island in North Carolina, killing the humans that visit the island. In this case, it's justified, since the island doesn't have the food supply to support them and they're starving, forcing them to hunt people out of desperation.
- Irwin Allen's execrable 1960 version of The Lost World climaxes in an encounter with a gigantic and voracious monitor lizard, although we're told it's a Tyrannosaurus rex. The movie also features a fight between another monitor lizard and a crocodile that are, allegedly, also dinosaurs.
- Skyfall: The casino in Macau has a pit with two Komodo Dragons in it. Later on, when Bond fights a bunch of Mooks while attempting to leave the casino, they tackled him into the pit. One of the Komodos comes out to watch them fight, and hauls one remaining Mook away by his ankle once he becomes distracted by trying to shoot Bond with a fingerprint-coded gun.
- Last Chance To See: Subverted in the Komodo dragon chapter; unsurprisingly, since the point was to raise awareness of the Komodo dragon as an endangered species. When Douglas Adams and Mark Cordwaine arrive there, however, they're surprised to find a tourist trail where a dragon eats a live goat that's been staked out for it. The tourists talk in fascinated horror about this monster, and how easily it could do the same to them, but Adams's own view is that the lizard is just being a lizard, and if you want to blame someone for the fate of the goat, then Humans Are the Real Monsters.
- In Redwall, most Reptiles Are Abhorrent, which holds true for the monitor lizards of Sampetra, who serve as shock troops for the pine marten Big Bad of The Pearls Of Lutra.
- Titan's Forest: Dayhunters are Understorian predators resembling immense monitor lizards. They are voracious, cunning and very dangerous predators with a taste for human meat, and are greatly feared.
- Jessie: Subverted, by Mrs. Kipling, Ravi's pet Asian Water Monitor. Whilst she is aggressive and scary, Jessie screamed when she first saw her, baring the occasional joke she's treated like just a big docile and slightly anti-social pet. She at one point saves Bertram and Luke, by eating a venomous spider that had invaded the apartment.
- Monsters Resurrected has an entire episode focusing on Megalania, a 6-meter-long prehistoric monitor lizard from Australia, which, like every animal in the show, gets the Prehistoric Monster treatment. Another episode covered the monitor lizards' marine relatives, the mosasaurs.
- Terra Nova: Subverted with the ancestral Komodo dragon, which is a vicious predator much bigger than its descendant and with a venomous bite, but easily warded off because it only targets weakened prey incapacitated by its venom. When Taylor intimidates it with a flaming torch it quickly retreats and doesn't return.
- In Pacific Mythology, Hi'iaka is tasked with bringing a young chief named Lohia'u to her sister, Pele (after the latter began to miss him after they hooked up at a party weeks before). Along the way, they face many adventures. In particular, Hi'iaka has to fight off giant monitor lizards with mana contained in her skirt. (Unfortunately for Hi'iaka, and more unfortunately for her friend Hopoe, this delays them quite a bit, and Pele gets jealous.)
- Averted in John Finnemore's Souvenir Programme, in which one sketch posits that the dragon confronted by Saint George was actually a Komodo dragon, and that they're good friends in real life. Saint George pretended to kill the dragon for publicity reasons, and the only conflict in the sketch is that the dragon has had difficulty getting a job since most people can't look past the dragon supposedly getting killed as a reason to give him a job. The two part on friendly terms, since the dragon is going to be hired to serve as a model for the national flag of Wales.
- In Armello's World of Funny Animals, the monitor lizard Volodar is the High Priest of a Rot-worshiping Religion of Evil. He's Affably Evil, but preaches the glory of oblivion to all who will listen.
- Conan Exiles: Komodo dragons can be found in the jungle in the south-eastern corner of the Exiled Lands (and, on some difficulties, the opening chamber of the Abyssal Remnant's dungeon), and are a threat about on par with the far-more-common crocodiles.
- Crash Bandicoot 2: Cortex Strikes Back: The Komodo Bros. are a Dual Boss, specifically two of N. Brio's henchmen that try to block your path from helping Dr. Cortex.
- Far Cry 3: Komodo dragons are just one of the numerous dangerous animals living on the Rook Islands. They can attack you from nowhere, and they take a ton of gunfire before going down. And that's not even getting into the much tougher Blood Komodo, which is constantly soaked in its strangely blood-red saliva.
- The Denser and Wackier spin-off, Far Cry 3: Blood Dragon, introduces the titular Blood Dragons. Cybernetic, dinosaur-like monitor lizards (maybe...) with mutagenic blood, which can shoot lasers from their eyes. They're by far the most powerful enemy in the game.
- Bilby by Dreamworks Animation opens with the eponymous bilby running from a hungry monitor lizard.
- George and Martha has a recurring character named Eton, who is a Komodo dragon. He is not malicious but rather creepy, and has a habit of popping up right behind George.
- Hey Arnold!: Zig-zagged with Helga's monitor lizard. The two seem to get along just fine, but the lizard itself is still an aggressive predator — something most notable when the school falls into chaos during Mr. Simmons's term as principal, during which the lizard can be seen in a hallway dragging a hapless student away.
- Kong: The Animated Series: In one episode, Giggles cyberlinks with a Komodo Dragon to become a pastiche of Godzilla.
- Kung Fu Panda: Legends of Awesomeness: Averted by Master Chao of the Sacred Onyx Council, an occasionally strict but generally benevolent kung fu master who appears to be an Asian golden monitor.
- The Lion Guard:
- Kenge is a rock monitor, who is aggressive, powerful and malicious. And who really, really dislikes being called little.
- Ora is a Komodo dragon who lives on the island the Lion Guard visits in the episode "Dragon Island". He's portrayed as a sadistic and ravenous predator, and at the end of the episode he makes an alliance with the evil leopard Makucha.
- Littlest Pet Shop (1995): Delilah the monitor lizard is a recurring villain and constantly plotting to eat the other animals.
- In My Gym Partner's a Monkey, the obnoxious hall monitor is a monitor lizard.
- The Secret Saturdays: Subverted with Komodo. He may be aggressive, but he's loyal and heroic. Played straight with his anti-matter counterpart, Komodo Monday, who's both entirely sapient and rather malicious.
- Star vs. the Forces of Evil: Septarians are identified as lizards and bear long jaws most similar to those of varanids. While not all are evil a few have been prominent villains, most notably Toffee.
- Total Drama Presents: The Ridonculous Race: "Got Venom" takes place in the Komodo Islands, and the first challenge is precisely to get some dragon venom. Owen gets temporarily blinded by the toxin, so he and Noah can't perform at their best and get eliminated from the race.
- In The Wild Adventures of Blinky Bill, Cranky the goanna is the tyrannical 'I Own This Town' mayor of Greenpatch and Blinky's constant nemesis.
- The Wild Thornberrys: One episode has Eliza wanting to meet a Komodo dragon. Once she and Darwin find one, it tries to eat them.