I don't mean to sound rude, but every year there are posts on the WDW boards and here asking this question. No disrespect to the OP, but unless you are hoping to cheat the system why would you care?
It's like going to a movie and asking if the theater checks for people sneaking into a second movie.
What type of reaction are you hoping to get? Honest people would be angry. My family goes every year and pays for our party tickets. At $60 a piece that's $420 for us. Of course we could try and think of clever ways to "sneak" a peek at the fireworks or parade, but what example am I setting for my children? Hiding in bathrooms, hiding our wrists, walking along the shadows, etc?
Most of the decorations and all of the overlays can be seen during the day. You are paying for the perks of shorter wait times, candy, fireworks, and a parade. If you can't afford it or it's seems too expensive just go and enjoy the parks during the day.