Here are a few sensible options:
1. Burn the car to the ground.
2. Attempt to remove it using a high powered leaf blower or vacuum cleaner.
3. Pour draino into the vents and hope for the best.
4. Attach an air freshener to your nose and wait for the carcass to rot and the bodily fluids to dry up.
5. Remove it yourself, by "having a go".
6. Pay someone to remove it.
Disclaimer: Do not actually try options 1 to 3, I take no responsibilty if you do so.