Docrates, a gigantic guy looking for Seiya and cia with the Dark Saints, running away when hearing police sirens. "Oh, no! The police!"
Seiya freaking out when Shiryu drags him out in the Gemini Temple and his befuddled expression as his friend explains the whole thing afterwards.
When Seiya and Shun arrive at the First Prison of Hades’ Underworld, they are advised by a Specter mook to remain in complete silence, in order to respect Lune, the current Judge of the Dead, who hates noises. Seiya then proceeds to make lots of loud noises, like sneezing and generally provoking the mook. This is made even more hilarious in the original Manga, where he actually farts just to provoke the Specter.
In the anime, there's the scene where Seiya almost tells the creator of the Steel Saints's clothes that they are the chosen Saints. What makes this hilarious is Hyoga covering his mouth and yelling at him — and they're both drawn in a borderline Super-Deformed style. Stuff like that is almost never present in the Sait Seiya media, so the Mood Whiplash makes things even funnier.