Anyone random show up?

I feel like I’ve asked similar questions in the past, but over the weekend we were with one of our close friends and he is single and we didn’t give him a plus one. He is sort of a free spirit so to speak and doesn’t always understand proper etiquette. For example, he didn’t RSVP, and he said yeah just put me down for chicken. I was like just go to the website and RSVP. He was like nah I’m not gonna do that just put me down for chicken 😂. I don’t mind because we know how he is and he really just doesn’t get it sometimes… So as we continue to talk he mentioned the wedding again and said yeah I asked so-and-so if she wanted to go with me to be my date, but she backed out so I was going to ask so-and-so but I don’t think I am....! I’m like… OK, well make sure you let us know whoever you decide to invite so that way they don’t just randomly show up and we don’t have chairs for them etc.


He said OK yeah I’ll let you know… The issue is that I can totally see him just showing up with someone without telling us. He’s a close friend, and we definitely can be more stern/straight up with him but i’m worried about other people possibly doing this too?? We’re seeing him Friday so we’re going to reiterate our point again about if he decides to bring someone to let us know by X date so we can add them on.
In addition to this, has anyone ever had people RSVP no and then show up? Would it be a good idea for us to add extra head counts on in case? I can really only picture a very SMALL handful of ppl doing this...(mostly some of FHs cousins).