When Hasbro's Mr. Potato Head made his debut in 1952, the main body of the toy consisted of a lowly garden-variety potato; well, more precisely, Mom provided the potato. What you got in the Mr. Potato Head package were the little plastic eyes, nose, feet, moustache, etc., that you stuck into the potato thanks to the sharp spikes on the back of each item. The toy stimulated kids' creativity because they could configure the vegetable man's features in any way that appealed to them - they could make him freakish or merely goofy, just by decided where (or if) to place the little plastic pieces.
Naturally, this didn't last very long, because parents became afraid that kids would hurt themselves with the sharp spikes, or perhaps try to rearrange their baby brother's looks with a little Potato Head creativity. (Plus, a lot of kids were forgetting to give Mom back the potato after play, so that the next time they opened the box, they found a disgusting, gooey mess.) So, the plastic Mr. Potato Head that most of us remember was introduced. Instead of kids being able to put any feature anywhere, however, the plastic body had specified grooves, while the little accessories replaced the spikes with plastic tabs that fit into the grooves. Thus, no longer could a child just stick things willy-nilly anywhere into the toy, but was forced to put the features into specified areas (although he could still mix and match which ones he used).
Over the years, of course, the basic toy has continued to change. The original Mr. Potato Head kit contained 70 different parts (just not, as has been noted, the potato). The most distinctive of these were a green cap, a bristly moustache, and a pipe. The pipe was done away with in 1987, due in part to the whining of nannying crybabies like Surgeon General C. Everett Koop. Other odd accessories were added or taken away over the years, such as bendable arms, different funny hats, eyeglasses, etc. One innovation came in 1983 when the Mr. Potato Head body was made hollow and fitted with a sort of trap door in the bottom, so that the plastic pieces could be stored within. In addition to Mr. Potato Head, the world has been introduced to Mrs. Potato Head, as well as their children, Brother Spud and Sister Yam.
The perennially favorite toy got a kick in the eye - er, pants - in 1995 when Mr. Potato Head became a prominent character in the successful Disney film Toy Story. The movie introduced an entirely new generation of youngsters to a classic item that their parents had enjoyed.
In recent years Hasbro has made themed sets available to consumers, consisting primarily of spare parts separate from the primary Mr. Potato Head package containing the body. These include such generic characters as Halloween, Princess, Pirate, Rock Star, etc. - basically different costumes for the potato character. There have even been Star Wars-themed sets, allowing our favorite vegetable toy to become Darth Tater or a Spud Trooper. The 2008 Indiana Jones revival film even spawned a playset entitled... you guessed it... Taters of the Lost Ark.