"I have to go online and search for special lights for my cousin's/wife's/mother's/brother-in-law's Seasonal Affective Disorder."
"I can't make it in today. My cousin stole my car." According to Jeff Foxworthy, this one works best if you live in a very small and very rural community.
If you live in Northern Canada you could try, "My tires are frozen to the driveway." or "My battery's frozen and my car won't start." or "My neighbor was trying to help me start my car and he's frozen to my driveway."
There's always the Dane Cook way. I remember watching a show where he was going on about avoiding a mate's party and he made up b/s about rolling his car into a ravine... Anyone seen it or could post a link? =]