The introduction to the trolls - especially in the few interactions before we see their faces (maybe their silhouettes or something like that), but mostly in general

With the fact we can see the other end for certain conversations, I'm really curious for some of the more excitable trolls. I like to imagine Karkat would flail around like a muppet being electrocuted during his rants for instance

or Terezi doing big exaggerated hand motions or something like that