The most similar one is the Bongo Cat thing, from what I can recall/search up.
No, this isn’t just banging on a flat surface, it’s a specific pattern. It does like ‘dun dun dun-dun-dun dun-dun-dun-dun dun-dun’. I’ve heard it throughout my life and from a bunch of different sources, so it’s pretty commonly known, but I still have no idea what it’s called.
I finished tagging the remaining D4DJ characters and added all of the Assault Lily girls. My best guess for the others in the back with Muni are perhaps Himari and Riri, but it's such little/unclear detail back there I'm not going to bother tagging them.
Regarding the fight in the background, Michelle is from Bandori and Tokyo Tower is a prominent symbol in Revue Starlight, but I'm not familiar with D4DJ or Assault Lily so I don't know what the other things are, aside from the daruma doll. If anyone knows what the metagross-looking thing is or the other thing holding the axes, I'd be happy to hear about it.
Context: On her 3D karaoke streams, Elizabeth is only willing to sing particularly spicy songs if she's using a character model that wasn't specifically made for her. I don't know where she got the one shown here, but what I do know is it's a free-to-use model that she chose because it only kinda looks like her usual avatar.
Added check translation because I'm not 100% sure my interpretation of the way Hachiroku is being addressed by Masamune is accurate. Once more info about these characters is released, I can use the added context to check the translation again.