* AccidentalInnuendo:
** In an early strip, Mooch recites the poem "The Owl and the Pussycat" to an actual owl, which includes the unfortunate line, "O lovely pussy! O pussy, my love, what a beautiful pussy you are!" It doesn't help that Mooch is a male.
* BrokenBase: While many praised ''Mutts'' for its messages, cute characters, and somewhat {{Retraux}} design, it has been criticized by many non-readers and cartoonists solely on its topics about veganism and spaying/neutering, with ''ComicStrip/PearlsBeforeSwine'' being a big example of this as it often made fun of the comic in a derogatory way.
** While Butchie becoming a vegan and its following storyline (a plan that WordOfGod had for a long time) made many readers happy, it was very displeasing with fans who had read the comic since the very beginning, believing the sudden change did not fit Butchie's character and personality.
* CargoShip: Mooch and the Little Pink Sock.
* EnsembleDarkHorse:
** Mooch. Many readers love him for his eccentric, flamboyant personality and his infamous speech impediment. The fact that [[CuteKitten he is a cat]] also helps. According to the official ''Mutts'' website's Comic Strip Archive, he's even starred in more strips than Earl!
** Guard Dog, representing the real-life guard dogs who more often than not are chained and left in bad conditions, is another popular character in the fandom. It's pretty easy to see why.
** Shtinky Puddin' (Jules), though not for the reasons you might expect.
** Despite appearing less often than the rest of the cast for obvious reasons, Sid the fish is adored for his cute design and his snarkiness.
** Sourpuss, because of his similarites to [[ComicStrip/{{Garfield}} another famous comic cat]].
** [[CheerfulChild Doozy]] is a cute girl that's quite popular with fans for her relationship with Guard Dog.
** Some people like Sourpuss's owner/Butchie's girlfriend for her overall cuteness and the way she interacts with Mooch and Earl, but especially Earl.
** Ms. Lulu, the pet physic, has only appeared in a handful of strips but she is another character beloved by fans, thanks to her "accurate" descriptions of what the pets are saying.
** Crabby's son, despite only appearing in several strips.
** Millie is extremely popular with older readers since [[KindheartedCatLover she's a cat person]] and the relationship between her and her husband Frank is relatable. In fact, the character herself is pretty relatable too.
** The various dogs and cats featured in the ''Shelter Stories'' strips. They even had an entire book dedicated to them!
* FanNickname: Crabby's son is sometimes nicknamed "Crabby Jr." by fans, due to his similarities to his father.
* FoeYayShipping: Mooch and Noodles, even though they ''can'' be friendly sometimes.
* GermansLoveDavidHasselhoff: While ''Mutts'' is not well known outside of its home country, it doesn't stop it from receiving fans every day worldwide.
** In 1999, five years after ''Mutts'' debuted in newspapers, the comic had a brief but notable popularity in Japan, due to many finding the artstyle and characters cute. It not only received its own action figures, but even a '''newspaper''' dedicated to nothing but the comic.
** ''Mutts'' is quite popular with Spanish-speaking fans on the Internet, a fan going by the username, "[=GatoProspero/Prospero=]" being a notable example.
* HeartwarmingInHindsight: ''Mutts''' topics about animal rights and the environment has made many readers change because of it. After being a vegetarian in 1990, four years before ''Mutts'' debuted, [=McDonnell=] became a vegan in 2005.
* HilariousInHindsight:
** This won't be the [[Series/{{Wishbone}} last]] [[WesternAnimation/{{TheSecretLifeOfPets}} time]] we get a talking Jack Russell Terrier as the main character.
** [[https://mutts.com/product/strip-072397/ This strip from 1997]] has Earl and Mooch meeting a ladybug, initially believing him to be a female but discovering that he's in fact a male (named Ralph). [[WesternAnimation/ABugsLife A year later]]...
* HoYay: Mooch and Earl, considering the fact that they're almost always seen together and act rather affectionate towards one another. They have also kissed each other, usually in human fashion, on the cheek or on the head countless of times. They have even given each other [[AffectionateNickname such nicknames]] (at least in the earlier strips) like "Moochie" and "Early", which they don't seem to mind at all.
** Woofie seems to love Mooch a lot and ''enjoys'' chasing after him and giving him lots of wet kisses, much to the latter's dismay.
* HumansAreTheRealMonsters: Probably not intentional but some of the more {{Anvilicious}} moments may have this effect.
* JustHereForGodzilla: The only reason why people even read ''Mutts'' today is to see Mooch act crazy, say [[CatchPhrase "Yesh!"]], or just act like a cat, which happens much more often than one might think.
** Some also come specifically for the biannual ''Shelter Stories''.
* PeripheryDemographic: While ''Mutts''' was created with everyone in mind, the majority of readers and fans are usually adult females, elderly women and cat lovers, which isn't surprising since most of them are only here for Mooch (see the Just Here for Godzilla example above).
** A surprising amount of preschoolers and teens (again female) love Mutts so much that the author has written several children's books just for them.
** Even PETA adores the comic and has praised it for its various themes and topics, which is understandable considering they're an [[AnimalWrongsGroup animal rights organization]].
** Just about any local animal shelter or rescue group who happens upon ''Mutts'', often using their strips on their websites as a way to educate and inform customers about adoption and fostering.
* TheyWastedAPerfectlyGoodCharacter: Because of the primary focus of animals and less on humans, some are barely seen or removed as a result.
** Dr. Woo, the veterinarian, who is the ''only'' [[TokenMinority Asian]] in a comic that features majority-white humans. She appeared in a story arc in which Earl goes to the vet to get his teeth cleaned and a year after her debut, [[DemotedToSatelliteLoveInterest is demoted to being Ozzie's girlfriend]].
** Mr. Grey, who debuted in an arc in late 1996. His only purpose is to be Jules' owner, appear ''only'' when he is looking for Jules and nothing else, despite having good potential for the strip. In the early 2000s, he disappeared without warning, never to be seen again, which might explain why Doozy is now Jules's primary caretaker.
** Sid. He was even advertised in the comic's early promotional material as being one of the main pets, along with Flip/Jilly. But because of the fact that he's in a fishbowl, stays in one place and is really only used for quick gags that require the characters to stay in one setting, he's often excluded in many illustrations and merchandise that feature the ''Mutts'' gang, even though fans had said they loved the character.
** Bushy is pretty much the quiet sidekick to Doozy who follows her almost everywhere as opposed to being a friend. And seeing she was encouraging passersby to adopt at the animal shelter, she could have been repurposed to be an AnimalLover similar to Doozy and even volunteer at the shelter.
** Babycakes/Eubie, Doozy's baby brother, was added to the strip sometime after ''Bad Baby'', another work from [=McDonnell=], had ended its run, though he was conceived since before ''Mutts'' made its debut. Babycakes could have interacted more with Earl and Mooch and even understand them at some point, but he disappeared in 2002 for unknown reasons and hasn't been seen since.
* ViewerGenderConfusion: Many pets or animals seen, with some exceptions, lack TertiarySexualCharacteristics, something that the comic tries to avoid, leaving readers to rely on context clues or characters' speech.
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