is it possible to sneak into welcome week without a macpass?

I dont think so. People who bought the Macpass have specfic shirts with you probably wont have, thus, you will stand out. So i doubt it. But I do know that some events are free to go to ( I dont know which ones).

No, not really. Passes are checked for most if not all events.

Plus, and maybe this is just my opinion, why would you want to? I know the price is a little steep but is it worth getting caught and marring your first experience at University? Not to mention all the other things like everyone else pays to attend these events and therefore by sneaking in and offsetting expected attendance you can actually drive up the price of tickets. I just think its disrespectful, especially for a first impression.

However, if money is an issue, I do believe there are events that are extended to anyone with a macID.