I think ive heard of the giant rat, but only once and i cant find the article again.
searched internet too; cant find any info.
for such a simple question this is pretty damn tough

Chriso123 is correct. Here's the proof, in the notes section:
http://www.uesp.net/wiki/Oblivion:Lazare_Milvan
Lazare is also kind of a big rat, as well.
It seems to me that it's Chriso123's turn.