Ignore the haters and naysayers.
If you really give it a go it might actually work.
When I was a teenager I worked in the mall and while I was working there someone basically hid in a the mall, waited until all the stores closed and robbed a few places. I think they got away with it if my memory serves me correctly. It would be more difficult with cameras now but not impossible, especially if you don't move around at all, just find a tucked away spot and stay there, when you move is when you will be at risk because then you might pop up on camera or trip a motion detector.
Go to a camping store and brainstorm what supplies you will need to deal with issues that might arise such as hunger, sleeping and needing to piss.
Bring a phone, a phone charger, maybe a book or two, a kindle, rechargers for your devices. If you can entertain yourself you will move around less And be less likely to get caught.
I honestly think I could do it. If you plan it and really, truly think it thru and prepare as well as you can (costumes, passing as an employee, maybe research what security there wears) maybe you could make it work. I doubt that the people running it have devoted a lot of attention to preventing someone from hiding out the day before.
make the most of your time there at weigh ins and find an ideal spot. Forget bathrooms, too obvious, and likely to be checked, walk around and find some nooks and crannies that no one will use, or dead space maybe under a stairwell or something- walk around and see what doors are unlocked, maybe you can find a multipurpose rooon not being used or a luxury box that isn't locked (they have to get in to clean them right? Maybe someone forgot to lock one)
Find someplace that no one will check or have any reason to access until fight day, then have a plan to blend in as a worker or continue to hide until gates open to the public.
Also- if you are going to do it, get good seats. No sense going thru all this trouble just to sit in the nosebleeds where you would have a better view from home
