Getting More out of One Panel: Overlays

An overlay is just what it sounds like: one picture laid over another. Used properly, it's both effective and efficient--in other words, you get more and you use less.

Japanese comics use it often and obviously, to a few different effects.

 Here, in Megumi Tachikawa's Kaitou St. Tail,  it's simply adding information about who is speaking. The character (Lina) wouldn't fit in the "shot" clearly enough to be recognizable unless you used 2 panels. Instead of wasting that space, the artist used an overlay to add the necessary "panel" or information. (You could count this as 1 and a "half" panels, since she breaks the panel border.)

Here's another informational panel-combination using an overlay:

Megumi Tachikawa's Kaitou St. Tail

Instead of "cutting" and flipping around the "camera" to see this important note, the artist simply made an overlay of the necessary information. The arrow pointing to the box also eliminates confusion as to where the note is or how we came to be looking at it.
See how efficient that was?
And wasn't it clear? No confusion --> effective communication.

An overlay can add more subjective information, too. Like how a character feels about a situation...

Megumi Tachikawa's Kaitou St. Tail

...or a person. (This one is from CLAMP, in Cardcaptor Sakura.)

The examples I've used here are Japanese, but it's effective in American comics, too (if less common).

 Here's an extremely effective emotional overlay (or underlay??) by Carl Barks.

 This one from Jake Parker's Missile Mouse #1: The Star Crusher is diagrammatic in nature, communicating where the main character is and the scale of the destruction he's creating.

I've used it, too, and it's really helpful.

 If you ever need to get more into a panel, this is a good way to do it.

Try it out!