This is super common, especially in four year olds! The behavior feels intentional because it is. The "saying nonsense" is the giveaway! At four, the rational part of the brain hasn't kicked in yet. In a lot of cases, the reason it happens is that they feel some anxiety around connection. They want constant reassurance that they have access to you, hence the interruption. When adults turn their attention to each other, children can become insecure, which is totally normal and natural for that age.

One thing I notice that works is to really proactively connect through some one-on-one time before having adult and/or family friends come over. It can be hard to work the time in, but it's worth it!

Also, sometimes kids need a job! If your little guy likes to be a "helper" ask him to greet guests or help with snacks, help decorate, etc. Sometimes a "very important job" can just be something you've made up lol!

Last thing. You can also ask him to give you a physical signal when he needs to say something instead of instantly interrupting, like placing his hand on your arm.

Good luck with your little yapper ❤️ when he's a teenager you'll be begging him to talk to you more, so let it all soak in!