Is there a word for the black "mess" between the yellow star and the green exclamation mark? And is there a unicode character/emoji for this symbol?
According to the "Lexicon of Comicana" by Mort Walker (still in print) the non-verbal "emanata" you want to characterize is referred to as a grawlix.
The bubble symbology was popularized by Walker who brought comics and comic strips "Beetle Bailey" and "Hi and Lois" to American newspapers for over 60 years.
Edit: It is artwork. There is no unicode for this glyph/icon/symbol currently AFAIK. At the rate they're being developed, however, it's only a matter of time before it appears if it hasn't already become part of some collection.