I'm going to invite more people to a concert, even though the person who invited me doesn't know them and doesn't even know they're coming.
Why would you invite more people like that?
I just want to make my friend jealous of all my other friends.
It is rude to bring uninvited guests with you, especially if the host doesn't know them. It's even worse if you're doing it just to make your friend jealous. You should reconsider inviting them and be kinder to your friend.
Nah, I'm going to invite them anyway.
Well, they probably don't have the tickets for that many people. The people you invited are going to be upset standing outside.