Hi, yes it's using the advanced dialogue plugin to fix a dialogue box to the bottom of the screen, this is wrapped in various if statements depending on variables, form selected, weapon equipped etc and loaded for each stage.
The avatars aren't actually avatars but are made up of four separate 8x8 ASCII characters, from special characters in the table that I wasn't currently using. There may be better ways to do it in newer versions of GB Studio, this one was made in v2.5.