When Queen Margo turns over on the massage table, one would initially think they saw a nipple slip, when in reality what you see is a white pastie - probably not common garb even for a spoof of a movie set in this time period.
When Xerxes threatens to write Sparta out of the the history books, Leonidas replies: "Well that's fine by me, Xerxes, because I can't read." Previously, he had read the name tattoos on Queen Margo's back, some of them out loud.
When Leonidas asks Queen Margo to marry him by writing "Marry Me" on her chest with a sharpie pen, the camera changes positions a couple times during the scene. The words disappear each time the camera switches to the wider shot.
When the Spartans stop to "replenish" their electrolytes, Sonio is tossed a bottle of red Gatorade. When they pan back to him after showing a few of the other warriors, the Gatorade in Sonio's bottle is blue.
When Leonidas breaks the glass to get the penguin spear, he shatters it in the middle. When he reaches for the spear in the next scene, the glass has been broken from the end (to make grabbing the spear easier).