Step Four: Non-Standard Balloon Styles
OK ... This time, I'm just going run through the various types of balloon you may commonly be required to use, and how to create them. If you've thought of an easier way to do any of these, please feel free to chip in.
One thing I can't stress enough, though, is that you should create these balloons as you need them. Simply having a master version and enlarging or reducing it as required makes it very obvious that you are using a template.
Hopefully, the example below illustrates why simply shrinking a pre-made balloon looks odd compared to creating a new one at the appropriate size:

First up, the most common two things you'll have to do (these should probably have been in yesterday's post, but never mind) are joined balloons and linked balloons.
Fortunately, these are incredibly simple!
For joined balloons, simply add a second balloon overlapping the first:

Our old friend Pathfinder -> Add Shape:

Result:

Linked balloons are an identical process, but you need to draw a linking tail between the two balloons:

Select the elements and Add Shape again:
Double Outline BalloonsStart with a normal balloon:

Using the DIrect Selection Tool (A) (white arrow - I'm going to assume you know the difference from now on) select the balloon but not the tail:

Switch back to the Selection Tool (V), hit CMD-C then CMD V to make a duplicate:

Hit CMD-Y to change the view to 'Outline' -- this makes it easier to place the new shape accurately over the one it duplicates:

In Outline view, the little 'x' marks that show the object centres should snap together when they get close:

Switch back to normal view - CMD-Y again. Using the Selection tool, hold down SHIFT to constrain the proportions and ALT to scale from the centre, and make the duplicated balloon a bit bigger than the one beneath:

Change the Fill colour to whatever you want:


Then use Arrange -> Send To Back:


You now have the result you want:

All you need to do is Group it:
Radio BalloonsThere are two common styles of 'radio' balloon, often used also for TV dialogue.
A simple jagged balloon, as shown in the example at the top of this post, is the easiest.
Draw an ellipse that will fit your text (which you should already have arranged into a nice block, remember!)

Then go to the Object menu and Add Anchor Points:


You may have to repeat this operation, possibly a couple of times depending on the size of the balloon, so I've set up an Action for this and mapped it to a Function Key.

Having increased the number of anchor points, all that is required is a Distort filter:


You need a negative value for this sort of balloon - turn on 'Preview' and just keep putting in number until you're happy with the result.

And apply to get the finished result:

The other style is more complicated. You still begin with your ellipse ...

Using the Pen tool, add a new anchor point on either side of the topmost existing anchor:

If you click on the original top anchor with the Pen, it should disappear:
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... And you can add two more evenly spaced anchors:

You then need to turn these two inner anchors from
curved behaviour to
corner behaviour. Select them with the Direct Selection tool, and then convert them to corners:

Using the Direct Selection tool, click on one point and pull it upwards:

Then pick the other inner point and drag it down by about the same amount:

Repeat at the bottom of the balloon:

Job done. Add a tail if needed.
Burst BalloonsThese are your shouty-screamy balloons. They're similar to the first radio balloon, but the effect is exaggerated, and deliberately made less regular.
Begin with an ellipse (or circle, or whatever shape you're using for a speech balloon) but rather than using 'Add Anchor Points', use the Pen tool to manually add anchors in a more random fashion:

Bring up the Distort -> Pucker & Bloat filter again and enter a negative value that gives a result that looks promising:

Don't worry. It won't look exactly right at this stage:

Using the Direct Selection tool, click on one segment of the balloon, so that the bezier handles appear:

Tweak both handles until this section of the balloon looks more, well, curved, and then repeat for as many sections of the balloon as it takes to get a result you're happy with:

Add a tail if needed.
Thought BalloonsThought balloons are very much out of fashion these days, but you may still come across them. They're basically the reverse of a burst balloon.
Start with an ellipse and manually add anchor points. Comicraft recommends placing these to divide the path into alternating short and long segments, with the occasional short-short segment to liven things up.

Then apply Distort -> Pucker & Bloat, but with a positive value this time:

Again, the result won't look right at first, resembling a flower more than it does a thought balloon:

Again, use the Direct Selection tool to pick up one curved segment of the balloon:

If you imagine the original shape of the ellipse, you want to pull these drag handles so that they would be roughly perpendicular to the circumference of that original shape. Work your way round the balloon, repeating as necessary. Yes, this is a faff.

Then add the thought 'tail', usually three circles of decreasing size, usually 'pointing' at the upper part of the character's head:
Whisper BalloonsSimilarly out of fashion (more generally denoted by lower case dialogue), you may still be called on to produce whisper balloons.
These are much easier!
Create a balloon as you would normally:

Go to the Stroke paletter and activate the Dashed Line option:

Fiddle around with the settings until you get a result you're happy with:
Weak BalloonsNot quite the same as a whisper balloon, the weak balloon is often used for injured, ill or dying characters. It's simply an irregular balloon with an irregular tail.
This is simply a matter of drawing a wobbly balloon with the Pencil tool:


Then draw a wobbly tail with the Pencil:

Then use the Pathfinder -> Add Shape function to make a finished balloon like any other:

This technique can be adapted for demons, zombies, vampires or similar simply by using one of Illustrator's custom brush strokes and applying it to an irregular balloon:
Robot BalloonsTo the best of my knowledge, only 2000AD uses the 'cut corner' style of balloon for robot speech, but we're all fans here, so I'm going to cover them anyway!
If anyone can think of an easier way to do this, BTW, please step up and say so!
Start with a rounded rectangle:


For some reason, you can't apply this next step to all the anchor points simultaneously, so select the two anchor points that make up one corner:

Go to the Convert Anchor Points buttons:

Again, for no reason I can explain, you need to click on the 'Curved' option first, then the 'Straight', and this should happen:

You can then use the Direct Selection tool to pick up all the remaining corner points in one go (shift-click for selecting multiple points) and repeat:

Add a tail as normal. I prefer curved tails for humes and straight ones for robots:

... And I think we're done for the day.
Tomorrow -- sound effects, including 'breakout' balloons (where the speech or exclamation breaks the border of the balloon ... you'll see what I mean).
Cheers!
Jim