I lowered my head, examining the surfaces of the tires, trying to look for some signs or hints of brown or black substances. After much smelling, I more or less concluded that the right side of the car was smellier than the left, so I examined it a little more.
Suddenly, at the corner of my eye, I saw 2 houseflies hovering around me. As the saying goes, "... like flies to rubbish," I figured that if I followed the flies, I would be able to find the 'rubbish,' in whatever form it took.
I traced their eccentric movements, and noticed that they frequently hovered around the front-right corner of the vehicle. So I scrutinized every single visible area for some signs of the source of the rancidness, all while continuing to strain my olfactory senses as I tried to use the acuteness of it as an additional aid, perhaps not for the wiser.
Not able to detect any visible sights, I decided to pop the lid of the engine, since it was the only possible area that I hadn't looked into. I looked at the mass of black and grey pipes and parts, not detecting anything out of place or close to a tint of brown. So I lowered my head and decided to rely on my sense of smell instead.
I strafed from the right to the left to the right again of the car engine, inhaling deep breaths of the offensive smell as I went along. "Whatever it is, it is surely coming from the right side, definitely the right side," I turned to her and said, before lowering my head to repeat the process again.
As I strafed from the right to the left and back to the right again, suddenly right in front of me I noticed something out of place. I squinted hard at it, under the shadow of the engine lid that was blocking out the light from the setting sun. There it was, caught amidst the winding pipes and parts, dark-brownish, furry and with its eyes tightly shut... a dead rat, caught between two parts of the car engine.

"Eew... gross," she said, as she took two steps away from the vehicle.
After numerous tries, she finally gave in and told the Maid to try pulling it out with a plastic bag over her hand. Murmuring about how smelly it was in her mother-tongue, the Maid wrapped a plastic bag over her hand and tried to use all the brute force she could muster to try pulling the little bastard out. After 10 minutes of yanking and complaining, we finally gave up.
Driving to the nearby petrol kiosk, we craftily decided to try to seek help under the guise of filling the tank. "Could you please help us check the battery water?" the Mother asked, setting the poor attendant up for a most grotesque encounter. As he popped the lid, we tried to ask, as non-chalantly as possible, "and could you please help us remove the rat stuck over there?"

But this illusion of merit was short-lived, as the foul-odour of my Christmas stocking continued to plague the car up till post-party on Christmas day, when I asked the Father to have a look and see what can be done about it.
After much examination, the Father finally decided to bite the bullet (like he always does) and wash the engine of the vehicle. After picking out loose bits of rat-fur, cleaning dried blood on the under-side of the engine lid and scrubbing the innards of the engine-parts, the engine was almost totally rat-corpse-free as I gave it one final olfactory-check.
Still detecting a faint odour, I peered deep into the innards of the vehicle to notice, wrapped around 1 of the pipes, a faint orange-beige tube-like object. I reached 2 of my fingers into the inaccessible area, and picked out the string-like object.
"I think it's 1 of the rat's intestines," I said in disgust, as I felt the squishy texture of the thing on the tips of my fingers through the thin layer of tissue paper.
"Seriously Dad, out of 20-odd years of driving and owning a car, have you ever had anything like this happen to you?" I asked the Father.
"Nope, not at all," the Father answered, with a slight chuckle.
With my jaw wide-opened in disbelief, I thought to myself, "Man, I must have been REALLY naughty this year."