Sebastian is a labrador - well, part of him is... he is the much-loved pet and a very important member of the Linton family. He exudes affection, enthusiasm and a vast joy for life.
This was such an enormous favourite growing up, I think my copy is entirely made up of loose pages by now I read it so often! (And it was second-hand and falling apart to begin with.)
ETA 27/04/12 - just re-read this because I'm on a bit of a childhood favourites kick! And it was still absolutely lovely, so much fun :) Sebastian is a great character and the Linton family are such a nice family to read about. Very reminiscent of a lot of the families you'd see on Aussie kids' TV series back in the 90s - just normal and fun and happy! Steve's little group of friends are also lovely to read about and I enjoyed revisiting this so much.
I also got huge a giggle out of 11-year-old Steve letting his friend Kerry (Ellis! Not kidding!) go first down the track in the bush... "it wasn't that he was being polite, he just hated walking into spiders' webs." LOL! So un-chivalrous, Steve!