why do pictures/people on widescreen tv's sometimes appear sort of squat? How can i avoid this?

In order to understand the answer to this question, you must first know a little background or info on the two main television standards. Standard definition programing, which is the standard format used for most stations and programming right now, is presented in a 4:3 aspect ratio. This means that it's pretty much a 'square' picture. For every 4 inches your screen is wide, it will be 3 inches in height.

The emerging technology for television broadcasting, however, is HD (High Definition) TV. This is presented in a widescreen, 16:9 aspect ratio. In addition to the wider format , which is actually closer to what humans perceive in the real world, high def programming offers many more lines of resolution than standard definition programing. The result: Crystal-clear, bright and vivid, colorful pictures, that look almost life-like compared to standard def programming.

Now, to explain your question...

When you try to display a standard definition 4:3 broadcast on a 16:9 display, you're going to have some un-used real estate on your television. In it's natural form, a standard definition image will not fill the entire screen of a wide-screen television. To compensate for this, a lot of TVs will "stretch" the image to fill the screen. Just like digital photo-editing on a computer...when you try to blow an image up, or enlarge it, you lose some detail, with the result being a slightly distored, or 'stretched' looking image.