Continuity mistake: This is repeated with all the main characters throughout the series: whenever someone puts on their clothes, their pants underneath change colour (for example, Seiya's blue jeans turn red).
Moero! Pegasus Ryuseiken - S1-E2
Other mistake: In the ending shot of the tournament bracket showing the potential future opponents, the two saints' names are written the wrong way, as "DORAGON" and "ANDOROMEDA", instead of Dragon and Andromeda. (00:22:00)
Kiseki no fukkatsu! Yuyo no cosmo - S1-E5
Trivia: When Seiya opens his eyes hearing Miho calling his name, behind her in the audience a particularly bored animator decided to put in some silly characters, including the Tin Man, the Lion and a girl with the look of Dorothy from the wizard of Oz. (00:19:20)