Frieza

Freeza's transformations bring in the idea that when a character becomes too powerful, their current physical form is nothing more but a limitation holding them back. In order to not only obtain, but contain this new-found power, the character must totally transform their physical body. In Freeza's case, he will go through a series of transformations that increase his over-all body size, and then end with a form that is just as tiny as his original form! Remember... size isn't everything! Oooh ho ho ho!

Frieza First Form
In his first form, Freeza generally confines himself to his hover chair and sends his henchmen to do all of the dirty work (namely collecting Dragon Balls). Freeza also wears a similar form of upper-body armor as seen worn on the likes of Vegeta, Zarbon, Dodoria, and the others. Freeza appears to be very small in height, which is shown to be true in the rare occasions that he emerges from his hover-chair.

There really isn't much more to say about Freeza's first form; he tends to just sit around and bark orders, not really showing much. His tail is relatively thick in width, able to crack the ground when slammed. His "helmet"-type head has two horns that protrude in near 45 degree angles. Freeza decides that he will transform and show off his further stages, though, when prompted by Vegeta... and so it begins...

Frieza Second Form
Freeza's second form is an almost complete opposite of his first form, in terms of general physical structure. The two horns on his head now protrude straight out to the sides, and then sharply both turn directly up into the air. Freeza's muscle tone is exponentially increased, which can be clearly seen on his chest and stomach areas.

Freeza's raw strength and speed also increase while in this form. Piccolo, after merging with Nail, appears to be at a near fighting stand-still with Freeza in his second form.

Many people confuse Freeza in his second form with King Cold (in his only form that the viewers ever see). Perhaps King Cold remains in a second-form, or perhaps King Cold is what an older, adult first-form looks like... we'll never know!