No, you can bring them over and register any time before classification, including Saturday morning. But people can claim an animal once it is registered - I claimed one that Friday night a couple years ago. I wanted to get him before anyone else did. =)
Claiming goes on during and until shortly after the show, so they can have their award and you can hear their comments if it helps you decide. However, it's not an auction, once they're claimed you can't out-claim on them, so the GSC and such may be claimed before the show even starts. Claimy claim claim.