Mr Rusty was the first EVER character in the Magic Roundabout show. Though he seems to sink into the background alot, he is still an important figure in the Enchanted Land. He is the mechanic of the Garden, anything that is broken, he can fix it. He is also the only one that runs the Magic Roundabout, making sure it stays in working order. In the first ever Magic Roundabout episode, Mr Rusty is upset because all the magic had left his beloved Roundabout. Zebedee arrived to Mr Rusty in a box, telling him that the magic would return to the Roundabout, if children rode on it once again. Florence and her friends (Dougal included) were brought to the Magic Garden by Zebedee, and have riden on the Magic Roundabout on a daily basis ever since, so allowing the Enchanted Land to flourish, and allowing other odd creatures to set home there, Dylan, Ermintrude and Brain, namely. So you see, Mr Rusty has an important role. If he doesn't run the Roundabout..well, we've seen from the movie what happens when the Roundabout breaks down, in a word: chaos.
His personality hasn't changed much from stock-motion to CGI form, I can't really think of any big changes at all. He cares about children, and goes out of his way to protect them. He loves his Roundabout more than anything in the world, and is able to play on his barrel organ as well as Dylan plays his guitar. To put it simply, Mr Rusty is a kind-hearted old man who wants to live a peacefull life running his beloved Roundabout.
On Dylan, Mr Rusty doesn't seem all that fussed. Unlike the other characters, he doesn't treat Dylan like a joke of nature, nor does he give the rabbit any grief for sleeping all over the place, often on a Roundabout horse.
"I can hear you, I'm only reading. I'm not asleep"
"Ahh, this is the life. It's so peacefull and sunny and...peacefull"
"I don't think you often have lettuce in panckaes, do you?"
"I was just oiling the Roundabout, needs oil, you know"
"Can't complain"
"Cows aren't easy to please"
"It's a long time since I felt energetic, very long time"
"I was very good at the hop, skip and jump in my youth, very good, indeed"
"People came for miles to see me do the hop, skip and jump..a rare sight. A rare old sight"
"It's out of control!"