This is by no means a comprehensive look at how Imaginext figures have evloved over the 13 years they've been in production. In fact, this is merely a look at two Imaginext figures I've picked up at the flea market over the past couple months, next to a modern Imaginext figure.
Regardless, it's neat to see how this line has changed over the years.
This odd looking lizard-man is dated 2005. Imaginext debuted in 2002, and this guy isreflective of the figures of that time. Other than a lack of a rotating head, he's articulated just like the Imaginext figures of today (both legs rotate together, shoulder ball joints). He's a bit less cartoony in design and smaller in scale, but you can see the Imaginext aesthetic that still runs through the line today.
This Troll (or perhaps a Ferengi) is also dated 2005. But as you can see, this is when Imaginext evolution took a bog leap forward. More cartoony and a little larger than his predecessor, Fisher-Price eliminated the leg articulation for a short time before they settled on today's design, although his 'footprint' is about the same as modern figures and he works just fine in the 'power pads' that trigger the action features of the playsets and some vehicles.
Finally here's the Alien Emperor from the blind bagged Series 1. I was disappointed that his brain inside the clear dome is just painted on the top inside and isn't a separate piece, but I got this guy for FOUR CENTS recently because my local Toys R Us must have swept behind a shelf or something and found two Series 1 blind bags. I checked the price scanner and they popped up at four cents each, probably the least I have ever purchased anything at retail for in my life. Sadly they only had the two, and sadly the other one was a lame racecar driver, but at four cents each who am I to complain?