The Battle of Thermopylae is always portrayed in fiction as only 300 Spartan warriors who bravely defended the Hot Gates for days on end, killing thousands of Persians until finally being outflanked by the Persian armies.
While the bravery and valor shown by Leonidas and his Spartans shouldn't be forgotten, they weren't the only ones present at the battle. There were 2000 more Thespians, Thebans, and Helots who refused to retreat with the bulk of the Greek Army and stayed to fight alongside Leonidas. Hell, the battle itself was a massive failure that only stopped the Persians for a short period of time. Leonidas didn't watch his flanks and paid for it with defeat. Alongside that common misconception, Spartan soldiers didn't break rank to fight alone and they sure as hell didn't go into battle without armor. They weren't male strippers for gods sake!