Oxidation
Oxidation
[Ponytail is holding a finger up in front of Megan while gray smoke and heat waves pours in to the frame from off-panel left.] Ponytail: In my defense, your car has been oxidizing since you got it. Ponytail: It's just happening a lot faster now.

In this comic Ponytail has set Megan 's car on fire, possibly by crashing it.
Oxidation refers to a whole class of chemical reactions. Any chemical reaction that involves the loss of electrons is called "oxidation" (since a lot of these involve oxygen). One oxidation reaction is rusting , the reaction of iron atoms in the steel of the car with oxygen and moisture to produce iron oxide hydrate. Rusting is extremely difficult to prevent, and all cars are rusting slowly. Oxidation was also mentioned in the title text of 1426: Reduce Your Payments , where the main joke was about the opposite reaction i.e. reduction.
Another oxidation reaction is combustion , an exothermic reaction, such as the violently rapid reaction of flammable parts of the car with oxygen to produce a whole load of nasty gases and particulates, as well as a lot of heat. Vehicle fires can burn very quickly and destroy a vehicle within minutes.
From the most detached viewpoint, these are both oxidation reactions (although they occur in different places: rusting normally happens to the car chassis while fires are usually isolated to the engine) and Ponytail argues that as all cars oxidize, the fire that she has caused has only accelerated the inevitable destruction of the vehicle.
This idea was already explored in the what if? Burning Pollen , where the second image shows a burning car and the text above mentions the difference between rusting and burning cars: Lots of materials oxidize when exposed to air. Bananas go bad, copper turns green, iron rusts. Fire is another kind of oxidation reaction. In other words, our cars are always oxidizing; we just try to keep it from happening suddenly. The title text of the image even mentions the fact that it is different parts that burns than those that rust: Although the parts that oxidize during a car fire and the parts that rust aren’t usually the same.
The comic by extension mocks arguments that ignore or trivialize quantitative differences. Such arguments are commonly employed to attack climate change: the Earth has been warming since the glacial period ten thousand years ago, it's just happening faster since the introduction of large quantities of greenhouse gases.
In the title text the small arthropods (invertebrates that have jointed bodies and exoskeletons) are referencing microscopic mites – tiny creatures that can live on the human body without normally causing any harm (you probably have eyelash mites , for instance).
Presumably as a form of revenge, Megan has caused Ponytail to become covered in much larger arthropods - most probably spiders , judging by Randall's fixation with them , but it could be any combination of these often feared animals: spiders, scorpions , insects , crabs , centipedes , millipedes etc. As contrasted with the harmless mites mentioned above, other parasitic arthropods (such as the Crab louse , an insect known in slang as "crabs") are notorious as a sexually transmitted infection , and Megan could have been referring to these as those Ponytail already had as a further means of degrading her after the car fire incidence.
Megan's car also caught fire in 1014: Car Problems , but there she did not at first know for sure who did it. Not a direct relation, but Megan seems to be unlucky with her cars.
This comic was referenced in the title text of 1732: Earth Temperature Timeline
[Ponytail is holding a finger up in front of Megan while gray smoke and heat waves pours in to the frame from off-panel left.] Ponytail: In my defense, your car has been oxidizing since you got it. Ponytail: It's just happening a lot faster now.
