Lanma:
Over the course of the books, Lanma's pigtail has developed a brain. It started out as a droopy, regular ol' piece of hair but now it changes with Ranma's expressions and is far from some stupid braid that hangs down on his back.

Female Lanma:
Is it just our imagination or does female Lanma always seem to have eyeshadow? Either that or Lanma as a male walks around with eyeshadow on just so he'll look like a normal person when he turns into a girl but I DON'T KNOW.

Ryoga:
Nine times out of ten, when we see Ryoga, it's a side view. And whenever it's a side view, he's being all wistful.
If you look at Ryoga's bandana in the first book, the knot is very high on his head and very small. Then, if you look later at it, the knot is as far down as it can possibly go and the bow thingys are all BIG and prominant when, at the beginning, they were barely there.

Mousse:
It doesn't happen all the time but Mousse's hair blows in an ominous wind more than anyone else's. And sometimes, his is blowing in the same panel that no one else's is.

Shampoo:
In the books, Shampoo has gradually gotten...I don't know...LONGER. It's kind of hard to describe but her eyes have stretched out and her legs seem extra super long and her torso is all...SMALL?! I know this may seem a bit psychopathic but I have most definately noticed it and it bugs me.

Akane:
In the beginning, after her hair was cut, it was small and contained and ball-like. Later in the book, she had a lot more hair and her side burns were VERY big. EVEN LATER, she appeared to gradually get shorter hair.
Akane defintely had the "tomboy" act at the beginning. While it was still kind of there, she later turned into more of a girl until she became the "damsel in distress" type girl.

Kuno:
Kuno used to be all mighty and great at Kendo but later on in the book, Kuno was a push over and Lanma would groan at the very sight of him. Genma:
Same pretty much applies here as with Kuno. Genma could match Lanma and he taught him stuff. Later on, Lanma was taught useless tricks if anything at all and Lanma could defeat him easily.

Nabiki:
Kasumi:
The IQ of the oldest Tendo girl, Kasumi, has greatly decreased since episode/book 1. At the beginning, she was saying things like 'Oh, he's younger than I am!' and pretty soon she's all like, 'Those two are such good friends!' when Ryoga had just run in and said how much he hated Lanma.

Ukyo:
Kodachi: