Self Demonstrating / Speech Bubbles

Hi Robot Buddy! Do you want to tell the nice tropers about Speech Bubbles?  
 <<Affirmative, carbon-based friend. Speech Bubbles are floating text circles (or other shapes) that characters in Comic Books and Web Comics or other dimensionally-challenged media use to communicate. That is all.>> 
Hold on there, Robot Buddy! There's just gotta be more to it than that!  
 <<Perhaps Professor Verbose has more data on this topic.>> 
  Why indeed I do! Speech Bubbles aren't just generic circles or places to put words, but metafictional constructs that can be painted, shaped, and written different ways! We can even superimpose them to show interruptions, if we were so rude as to interrupt!
 <<This is illogical and serves no functional purpose.>> 
  Oh, silly Robot Buddy! Your logical mind hasn't noticed one of the greatest uses for Speech Bubbles. In fact, your own speech bubble is different from young Tommy's and my own.
Whoa! That's cool! But, why are they different?  
  Yes, it is indeed "Cool" Timmy! Differently shaped and even colored or fonted bubbles are nature's way to help readers notice who's saying what more easily, as well as how they're feeling and even if they're robots, as your Robot Buddy's bubble shows. In fact, some species even use Rebus Bubbles at times!
 >>Warning! Warning! Logic circuit malfunction! Switching to mode: Crush. Kill. Destroy.!<< 
Gee willikers, doc! Robot Buddy has gone berserk!  
  Yes, and if you'll notice, both your own and your robotic friends' speech bubbles have changed to show your excited emotions! Now, to hit the "Off Switch"...
 >>Crush! Kiiillll.... deessstroooooy... >> 
That was a close one, doc! I've never been more scared in my short fictional life!  
  That certainly was, Jimmy! Just remember that things can always get scarier! For example, some villains and monsters like to use black speech balloons and strange colored text. If I were to change my speech bubble just so, and highlight it with a mouse...

  Billy? Where did you go? Oooh, tears!