Me and a good friend use to sneak into arco in the early 2000's, probably not even an option at the G1C. You know, the whole "act like you belong and they won't bother you" kind of sneaking in........
I did that once at the original ARCO during the 86/87 season. It was kinda easier due to the layout and setup of that smaller building.
Michael Jordan didn't play in SAC during the inaugural 85/86 season, and by the next season the "Air Jordan" hysteria was at a fever pitch. I didn't have tickets to the game, but talked my poor mother into driving me out to ARCO so I could try to get MJ's autograph.
One cool thing about the 1st ARCO was that the visiting players had to exit the building to get to their bus. We knew where that area was, which was right next to one of the fan exit points. We got out there early in the 2nd half and I noticed a few people exiting early for whatever reason. I told my mom if it happens again I'm gonna grab my younger sisters arm and go inside as the people are exiting. Sure enough, a few moments later the door opened and we just went right in.
We got to see much of the 2nd half. MJ scored 40 that game, with some highlight dunks. For some reason, I never tried to sneak in again that season. The next season the newer ARCO opened. The opponents bus was inside the building behind a roll up door. So the 1st two seasons of fairly easy autograph seeking went up in smoke.
On a side note, my hunt for MJ's autograph that night ended up in vain. He exited the building surrounded by a half dozen or so security guards and got right on the bus. I think the next night in Portland he was chased by fans, so the extra attention and precautions were certainly warranted.