Notice this all the time with regular clothes too. I mean, how many times have you put a t-shirt on inside out and just rolled with it all day? It's like when you're in a hurry, your brain just skips the basic checks. With cosplay, it's even worse because you're so focused on the look that you miss the simple stuff. Maybe it's just me, but those little mistakes make the whole thing more human and funny.

aaron_cooper is right about the lunch crowd, but I'd say get there right before it peaks, like 11:30. The sardine lines get crazy (trust me, I waited 20 minutes once). Also, try the pastel de nata from the bakery stall near the entrance, it's fresh out of the oven then. You'll have a better experience without the full rush.