I'm going to bring people who weren't on the guestlist to a birthday party
Do you think that they will be let into the party?
I don't think they can stop them and there will be a big fight. They will make the party worse.
I understand what you mean, but don't bring anyone to the party that wasn't invited. The party will be much more fun without the unnecessary drama.
But the more the merrier.
I think that you should talk it over with the host first. I think that unless you do that, it is not okay to bring people that were not invited.