For those who read or even flip through the manga, has anyone noticed that Sesshomaru's mokomoko-sama grows longer? At the beginning it hangs off the ground, but as the story goes on, it is dragging on the floor like a blankie! Also, his doggie ears seem to grow in length too.

Sesshoumaru's facial features also became more masculine, and his hair lost volume. All of the characters went through some sort of change as the manga went on. This happens in any manga that's longer than two volumes. The artist either gets better or gets lazy, and changes occur.

Sesshomaru's attitude seemed to have changed as well. From what I recall in episode 5-7, 18-19, and 35-36, he seemed more 'talkative' and expressive (he chuckled in episode 18.)

The Sesshoumaru in the manga comes off alot more maniacally playful than his more stoic self in the anime and his attitude changes are just his character developing. As for the changes in his mokomoko: Ive heard one theory that maybe the mokomoko holds excess energy, this would explain why it grows bigger through the manga as he is gaining power thus the mokomoko needs to hold more(this hasn't been confirmed it was just a theory I saw on the forums a while back). I also think it might be just RT's hand becoming more familiar with drawing the character too and slowly he gets more defined and such, along with her also wanting to change the image of him because of his inner changes. (same a Tomosaho's theory on it)

Sesshou in the end of the manga looks way hotter than sesshou in the begining of the manga though, doesn't he?

Look at the fluff *is jealous of Jaken*

Maniacally Playful? That phrase just made my morning! XD I got the manga panels to prove it to! Although he seems less 'playful' and more serious as the manga goes on, but I guess that's part of maturity.

Sesshou in the end of the manga looks way hotter than sesshou in the begining of the manga though, doesn't he?

That he does.

Edit: Although come to think of it, ALL Dog Demons are probably playful. Inupapa was rather frivolous with Izayoi, Inuyasha couldn't resist going after a stick thrown by Kagome, and Sesshomaru (in a twisted macabre way) enjoys teaching his 'dear' little brother to respect him.