Ancient Grome

A sister trope to Mayincatec, Spexico, Far East and Scotireland, a tendency for writers to overlap the Greek and Roman civilizations and confuse aspects of the two, e.g. Roman numerals in an otherwise Greek setting, Greek Gods in Rome, and vice versa, etc.

Partially caused by Did Not Do the Research, but this is Older Than Feudalism as it was primarily the Romans' own fault when they drew a lot from the Greeks (Classical Greeks, that is; contemporary Greeks were more likely to end up as the butt of jokes for being failures and rather demotic). One of the most famous examples that immediately come to mind is Classical Mythology. The Romans would also continue placing plays in Athens or other Greek cities, to avoid slandering the state, but leave everything else Roman-like. Also, due to massive Greek colonization (mainly before the rise of Rome), a large chunk of southern Italy was known as Magna Græcia (Μεγάλη Ἑλλάς, Megálē Hellás) -- "Great Greece." Greek was also the most commonly spoken language in the greater Roman empire; Latin was the official language of Rome itself, but Greek was the lingua franca spoken by non-citizens, at least in the eastern half of the Empire. The vast majority of the New Testament was originally in Greek as a result, as they were written for a diverse audience living under the Roman empire.

It would probably be valuable to note, at this point, that "Ancient Greece" is itself a lesser example of Cultural Blending; see Ancient Greece.

When Ancient Grome meets language, you get Canis Latinicus.

Has nothing to do with Gnomes from ancient civilizations, or with the King of the Earth Elementals in the Elric of Melnibone universe, and the other title choice -- "Ancient Reece"—would have been even less indicative due to sounding too much like a slang term for stale peanut butter cups.

Anime and Manga

 * Fate Stay Night uses the Greek names for its ancient Greek characters (this is the usual convention in Japanese), but if the Roman name is more common, every translation, fanmade or official, is likely to change it to that (e.g. the original uses Heracles but the subs say Hercules).

Comic Books

 * Marvel's Incredible Hercules: Two different explanations have been provided in the comics for the use of his Roman name when everything else is drawn from the Greek myths. The first was that Herakles is his real name and Hercules is his "superhero" name, since that name is more familiar to Americans. This was later retconned into his having changed his name to distance himself from his stepmother Hera (since Herakles means "Glory of Hera").
 * DC's Amazons: The Golden Age Amazons as created by William Marston had a ton of Roman stuff, including the gods going by their Roman names (Mars, Venus, and Minerva most prominently; hence "Merciful Minerva!"). The Post-Crisis rebooted version stripped out all the Roman stuff (Mars becoming Ares, for example), except for Diana's Latin name, which was justified as her being named after a female pilot named Diana who crashed on Themyscira in the 20th century. This has also been lampshaded on several occasions, such as when a bunch of Neo-Nazis invade Themyscira and comment that some of the statues look vaguely Roman.
 * In one story, we're told that the Greek gods created the Roman gods as avatars, but they gradually developed into independent beings with slightly different personalities. This leads to Zeus/Jupiter becoming one being again, and insisting that the others should all do likewise. But that was one Cosmic Retcon and several "What the hell's going on with the Greek gods now?"s ago, so probably isn't canon any more.

Film

 * The Matrix: The Oracle has a reference to the Oracle of Delphi (Greek) over her door, but it's written in Latin.
 * The historical adviser on Alexander mentioned an earlier attempt to make a movie on the Great man, where the researcher informed him she's taken pictures of a lot of statues in Italy, where Alexander the Great never went in his entire life.
 * Although the Romans copied heavily from the Hellenistic sculpture style, and the most famous statue of Augustus may actually be a statue of Alexander with a new head. So somewhat justified.
 * Also, some of the most artistically distinguished and well-preserved Greek architecture and art can be found in former Greek colonies, most notably southern Italy and Sicily.
 * Lampshaded by the protagonist of the Soviet film The Pokrovsky Gates: "My name is Konstantin, which is Classical for "steadfast".
 * The Clash of the Titans remake shows Greek soldiers in Roman armour and weilding gladiuses.

Folklore and Mythology

 * A lot of mythological Greek characters that Rome borrowed are known either by one or the other, even when set the "other" culture. Many of their Roman names are now Forgotten Tropes. Despite the planets of our solar system being named after them. Or perhaps because of it; through a One Mario Limit effect, "Jupiter" and "Mars" have too great a tendency to call the planets to mind for a modern hearer.
 * Hercules: Best known by his Latin name, despite being a Greek hero. His Greek name was Herakles, which is sometimes written as Heracles in English, both in works of fiction featuring him such as the Glory of Heracles Video Game series and reference materials related to Greek mythology. If you want to be especially correct, it would be written as Ἡρακλῆς, because it's hard to please everyone when using romanization.
 * Even if the author does the research this can become a Translation Convention; there are a lot more people who recognize the name "Hercules" than "Heracles," and we don't want to confuse the audience, now do we?
 * Zeus: Rarely, if ever, called Jupiter, or Jove.
 * Except in the somewhat archaic phrase "By Jove".
 * Athena: Her Roman name is Minerva.
 * Ajax is the Latin name for the Greek name Aias. This gets very confusing in The Iliad because translators have various ways of referring to the two Aiantes...Ajaces...two people named Ajax.
 * All the Egyptian gods are usually called by the Ancient Greek versions of their names, not the actual Egyptian.
 * Exactly. For instance, the far more popular Greek translation of "Anubis", compared to the original Egyptian name "Anupev".
 * Try reading a book of Greek myths that uses only the Roman names? (Greek names were only used in the Greek-to-Roman name chart.

Literature

 * In the Alexander the Great trilogy by Mary Renault, the main character is referred to as "Alexander" (his Roman name), even though the rest of the characters are called by their Greek names rather than their Roman ones e.g. Cassander becomes Kassandros, etc. Word of God justified this on the basis that the reader was more familiar with the Roman name, and it helped differentiate Alexander the Great from the two other prominent Alexanders in the novels (who go by "Alexandros").
 * Occasionally she used a flat English translation, e.g. "Oxhead" for "Bucephalos" (Alexander's horse), whose name meant, well, "ox-head".
 * Ditto many ancient Greek texts. Among scholars of the ancient world, it's more common to hear about "Plato's Republic" than "Plato's Politeía," and more common to hear about "Aristotle's De Anima" than "Aristotle's Perì Psūchês."
 * It's also more common to hear about Plato than Platon and Aristotle than Aristoteles.
 * "Republic" is a separate issue: it's a word in English, not Latin. It derives from, and sounds a lot like the Latin "Res Publica," two words that idiomatically mean "state" or "commonwealth," but it's really more like calling it Aristotle's Poetics rather than Περὶ ποιητικῆς or its Roman alphabet equivalent. "De Anima" is a more straight example, since the words are actual untranslated Latin.
 * In Everworld, All Myths Are True, so we get both the Greek and Roman pantheons, who hate each other. Neptune and Poseidon are always beating the crap out of each other, and Zeus refers to the Romans as "that impostor Jupiter and his brood".
 * In the Middle Ages, everything that western Europeans knew about Greece was filtered through Rome, in the form of Latin translations of Greek texts. The legacy of this was long-lived. As late as the 20th century, English translations of Homer normally used the Latin names for all the characters. Otherwise, James Joyce's Ulysses would've been called "Odysseus".
 * As would Tennyson's poem.
 * Star Trek: New Frontier lampshades this by saying that the superpowered Beings used to be both Greek and Roman gods...as well as Norse, Hindu, Egyptian...and Santa Claus.
 * Somewhere, the 4th-century bishop of Myra, in Asia Minor, is throwing up his hands and saying "I don't know, you tell me."
 * The sequel to Percy Jackson and The Olympians, The Heroes of Olympus, shoots this trope to hell by making very clear distinctions between Greek and Roman mythology.
 * Aleksandr Zarevin's Lonely Gods of the Universe reveals that the Greek and Roman gods were, in fact, inspired by Human Aliens from the planet Oll. The Ollans didn't have any special powers (except immortality and red hair) with the exception of Hera's prototype, who learned advanced hypnosis from Atlantean priests (to the point where she can literally stop someone's heart with a look). There was also Mars Ares, a security guard who brought his gun with him and taught the Atlanteans hand-to-hand combat and military tactics. When Atlantis sunk following a comet strike in the Mediterranean, the survivors fled to the mainland, including what would become Greece and Rome.

Live-Action TV

 * Buffy the Vampire Slayer has Greek Gods, Roman Gods, Egyptian Gods and a few more. The only god that isn't included is the Christian/Jewish/Islamic God due to Joss not liking him.
 * Battlestar Galactica (the 2000's version): has Greek and Roman themes side by side.
 * Not to mention there are several gods who are referred to with both Roman and Greek names (Jupiter/Zeus, Mars/Ares). It's probably a cultural/linguistic thing.
 * Interestingly, while the Tauron language is revealed on Caprica to be Ancient Greek (or more likely represented by Ancient Greek), the Taurons consistently refer to their chief/patron god as "Mars" rather than Ares. Of course, the Greek Ares was a tremendous bloodthirsty dick who was the closest thing the Greeks had to an evil god (Hades actually being quite a decent fellow), while Mars (fittingly for the conquering Romans) was rather more positive.
 * Whose Line Is It Anyway? had a show where they were playing the game "Questions Only?" set in ancient Rome. Josie Lawrence asks Stephen Fry whether he's going to the Parthenon tonight. He asks Clive Anderson to please tell her the Parthenon is in Athens. Which results in Josie feeling 2 feet tall.
 * They say of the Acropolis, where the Parthenon is...
 * (For the record, the similarly-named Pantheon is in Rome.)
 * In MythBusters, "Episode 153 - Arrow Machine Gun", Adam mistakes a Roman helmet for a Greek Spartan helmet and a Greek hoplite as a Roman legionary.
 * In Hercules: The Legendary Journeys, the title character is called by his Roman name, but all the gods except Cupid have Greek names.
 * The Russian translation corrects this by calling him and the show Herakles (although, dropping the "es"), which is more known in Russia than Hercules, which most people there think is a brand of oatmeal. Cupid probably remained, likely due to Eros not sounding very family friendly.
 * Xena: Warrior Princess: One episode was devoted to Bacchae, and thus featured Bacchus in a major role. As opposed to, say, Dionysus.
 * Dionysus also exists in the setting as a completely different character.
 * And let's not forget Xena's enmity with Julius Ceasar (although that may have more to do with Anachronism Stew, seeing as she met up with the biblical Abraham a few seasons earlier).
 * An episode of Sabrina the Teenage Witch saw Sabrina borrowing ice skates from Mercury who was on the phone to Minerva and later on, Zeus shows up. Insert facepalm.
 * Also a book written from the show featured the Pid family arriving in Westbridge from Greece. The son Quentin is actually Cupid while his parents are Martin (Mars) and Veronica (Venus). And then for some reason Q. Pid said that Valentine's Day cards with Cupid on them are actually reproductions of his baby pictures.

Music

 * Taken to an extreme in Igor Stravinsky's cantata Oedipus Rex, which is entirely sung in Latin though based on an ancient Greek play.
 * The name "Oedipus Rex" is itself a bit Groman, since Rex is a Latin word. The original Greek was "Tyrannos."

Theatre

 * Shakespeare's Timon of Athens: Justified, in that not much was known about ancient Greece at the time.
 * Also very prevalent in Shakespeare's "Pericles, Prince of Tyre", which takes place in various locations in Greece, but uses only the Roman names for deities; those mentioned during the course of the play include Diana, Priapus and Juno.
 * Thespis, the now lost operetta by Gilbert and Sullivan, takes place on Mount Olympus but uses the Roman names for the gods. Made stranger by Gilbert's claim that "The time is the present day, the place is Ancient Greece"
 * The Harburg musical THE HAPPIEST GIRL IN THE WORLD is loosely adapted from the LYSISTRATA of Aristophanes and set in ancient Athens, but uses the Roman names for the gods.

Video Games

 * In God of War III, the Spartan protagonist faces off against the Greek gods...and Hercules (rather than, say, Herakles).
 * Considering that Hercules's voice actor is Kevin Sorbo, is more like an Actor Allusion to Hercules: The Legendary Journeys.
 * Word of God claims this was because the Roman name is better known (thus why the name "Hercules" shows up in move names in the previous two games made long before Sorbo was cast)
 * City of Heroes allows characters to explore the zone of Cimerora through time travel. It's largely Roman, but there are a few details that are Greek.
 * A few stages of the NES game Day Dreamin' Davey are all revolved around ancient Greece (especially Mt. Olympus), but the game's walkthough and The Angry Video Game Nerd mislabel each of these stages as "Ancient Rome" (though we have to admit, one upgraded bow has the name of the Roman god Mars, rather than the Greek god Ares).
 * Altered Beast has Zeus ordering the protagonist to rescue his daughter Athena, in a landscape resembling Greek temples... and yet the protagonist is described as a Centurion, a rank of the Roman Legion.
 * Eight Realms lumps together Greek and Roman elements into one civilization for the Classical age.

Web Comics
"Justin Pierce: Generally speaking, most online comics get by with no editorial management, but in this case I made a couple of Greek jokes regarding Pompeii, a Roman city nowhere near Greece. I will leave the comic unchanged for the weekend as a shameful reminder to do better fact-checking, then replace it on Monday with a version that addresses my Carmen Sandiego dilemma."
 * The Non-Adventures of Wonderella. On March 17, 2012, Justin Pierce uploaded the comic "Win, Lose, or DRACHMA". Shortly afterwards, he realized that Greek jokes made no sense in a comic was about the Roman city of Pompeii. So, two days later, he replaced it with an edited version of the comic, retitled "POMPEII as You Go".

Western Animation

 * Disney's Hercules: Set in mythological Greece but mentions gladiators and uses Roman numerals and Roman Name. BUT he gets an "alpha-plus" as a grade in the series, so everything works out fine.
 * One episode has the founders of Rome calling for gods to sponsor them. They settle on the Greek gods, on the condition that they use the names the Romans picked out for them. They agree, although Hades is vehemently against being called Pluto, a name he wouldn't even give his own dog.
 * Which is in itself an example of Not Doing The Research, as Pluto was simply a Latinization of the Greek Πλούτων (Ploutōn), the god's actual Roman names being "Dis" or "Orcus."
 * In the film, when Pain and Panic are pretending to be children needing Hercules to rescue them, one uses roman numerals by pleading "somebody call IX-I-I" (saying each letter).
 * In another episode, a mailman arrives with a package for Herakles, and Herc "corrects" him.
 * In yet another episode of the animated series, they introduce the god of pleasure and call him Bacchus (Herc wants to throw a "Bacchanale") -- that's the god's Roman name; his Greek name is Dionysus.
 * Bacchus was, again, simply a Romanization of Greek Bacchos (Βάκχος), an alternative name for Dionysos—who was not even a Greek god to begin with, but was imported from the East, much as Isis was later imported to Rome. The native Roman name for the god of viticulture was Pater Liber, the "Free Father," who was identified with the Greek Bacchus much as Iuppiter=Deus/Iovis Pater ("God/Jove the Father") was identified with Zeus, father of the gods.
 * The use of Roman numerals is likely due to most people not recognizing Greek numerals, making θʹ-αʹ-αʹ less understandable than IX-I-I.
 * Batman the Animated Series: At the end of the episode "Fire from Olympus", Maxie Zeus identifies Two-Face as Janus, a Roman god, despite imagining himself to be a modern incarnation of a Greek god and imagining Joker as Hermes and Poison Ivy as Demeter. Of course, he is out of his gourd by this point...
 * Note too that Maxie Zeus, beyond being crazy, is also never really mentioned to be well-learned. So it may be as much as his own ignorance as anything else (ie his delusions are as much pop culture and knowledge as fact).
 * An early episode of Arthur has Francine create a comic depicting the Olympic games... for a school report on Ancient Romans. This, as well as her suggestion that they could be "Roman athletes at the Greek Olympics" causes Brain to ask her, "Didn't you do any research?"
 * Well, the Romans were allowed to compete in the Greek Olympics, but if the report has to be about ancient Rome, that does not help much.
 * Subverted on Phineas and Ferb by way of Brick Joke: the episode "Greece Lightning" has the characters play gladiators and put on a chariot race after learning about them at an ancient Greek exhibit at the museum. Then we go to a commercial, and the next fifteen-minute episode, "Leave the Busting to Us," begins with Ferb stating, out of the blue, that "gladiators were Roman, not Greek."
 * Played with in Total Drama World Tour, when Chris announces that they are going to Rome for their Olympic challenge. When several of the contestants inform him that the Olympics are Greek, he gets annoyed...and then has an intern thrown out of the plane for giving him wrong information.
 * For added points, he then takes them to Athens. No one mentions that Olympia is a different place. (Heck, Owen's guess of "Mt. Olympics" was actually the closest...)

Real Life

 * A common mix-up, mostly by drunken college kids, is the use of toga in a Greek setting. Togas were a Roman article of clothing, the Greeks wore chitons, not togas.
 * And the toga was the equivalent of the three-piece suit, almost never worn in convivial settings.
 * The "togas" often resemble (very crude) approximations of Greek garments anyway—often the exomis, a rather revealing garment that leaves one shoulder and part of the chest exposed. An actual toga has around 20 ft of cloth, and is wrapped around the body several times.
 * There was a time when Greece and the Roman Empire were synonymous, i.e., the eastern Roman ("Byzantine") Empire. However, the empire existed during the Middle Ages. Medieval Grome, anyone?
 * To elaborate a bit: Greece was conquered by Rome circa 146 BC. While Latin remained the official language of the whole Roman Empire for a long time, the lingua franca of most of the people in its eastern half remained Greek. After the empire was split in half in 293 AD and the western half fell to German barbarians in 476 AD, Greek began to replace Latin in most official contexts of the eastern half. Therefore, the Byzantine Empire was essentially a Greek-speaking Roman Empire until its demise in 1453.
 * Greek itself was considered a language of prestige and learning in the Roman Republic and the Roman Empire for a long time, much as Latin was in modern contexts.