Plopmen rarely talk. They don´t have many topics to talk about- there is only one actually. It´s always like two plopmen meet each other by happen in the void of their planet and start talking about the sense of their existence.
They have an aerial in their head wich appears when they notice the other ploplmen want to talk to them. And they talk and talk... But they don´t make any sound while talking. It´s on the same purpose like when our bats look for their pray.
When they get angry, they just make ugly face and turn their aerial.
You may be surprised but these creatures can argue a lot! If someone has a different opinion on their sense of life, they get very angry.