Over the years, I got a lot more creative killing off friends of my parents (it made me look more sensitive), cousins, great aunts (they're always good because they're hard to confirm or deny), and second cousins, once removed (nobody really knows what that is, but it sounds good). The key is to keep track of who you killed off for whom. You never wanted to kill off the same person to the same teacher.
Speaking of dogs and homework; If my dog ate enough of my homework growing up, could he have gotten lead poisoning from all of the papers he ate? Now, that would be cool, combining two excuses into one. My dog died because he got lead poisoning from eating my homework assignment.
And then my fat, great aunt tripped over my dead dog breaking her leg, landing on my second cousin crushing him on the spot. That could be good for a week!
There isn't any lead in pencils? OK, my dog choked while eating my homework assignment.... We'll call this the Ferris Bueller defense. Research for some of these excuses is harder than homework.