Porque Chihuahua faz isso na vida real também e principalmente não há nenhuma preocupação séria lá. De petchidog.com :
It is not uncommon for a Chihuahua puppy or dog to shake. Some refer to this as trembling or shivering. In fact, so many Chi's shake that some mistakenly believe that it is a trait or characteristic of the breed. It is very common, however there is always a reason why, and there are steps that you can take to stop or at least decrease the shaking. -
Ruling out Health Conditions which cause it :
If a Chihuahua has sudden and violent shaking, one must rule out poisoning. This may include the ingestion of certain foods (chocolate and raisins are two toxic foods that dogs may ingest), or other common poisons including household cleaning solutions, insecticides, or human medication.
While this must be mentioned as a possible reason for trembling, kidney disease or kidney failure is a very serious health crisis that involves many more signs aside from shaking. Some of these are: pale gums, mouth ulcers, bloodshot eyes, an odd ammonia smell (due to a buildup of waste products in the body), weight loss, a dulled coat, weakness, difficulty breathing, disorientation, and loss of balance.
If you suspect an ear infection, veterinary care is recommended. A Chihuahua's ears may need to be flushed out and medicated drops given.
When a dog is moderately to severely injured he may shake uncontrollably due to the shock of trauma and/or pain.
The Most Common Reasons Why a Chihuahua Shakes
Low Blood Sugar
What happens: This breed tends to have a high metabolism and in turn is prone to dips in blood sugar levels. A minor dip can cause shaking. A severe dip will cause other symptoms including drowsiness, confusion, and even fainting.
To help prevent this: Chihuahuas of all ages should be fed small, frequent meals and snacks. Most Chi do best with 3 small meals per day and 3 to 4 snacks. Distributing the food in this way allows the body to receive a steady supply of fuel and nutrients.
What happens: This breed - due to its very small size and low fat-to-muscle ratio - has a hard time regulating body temperature. Even if you feel just fine, there is a good chance that if your Chihuahua is shaking, that your dog is feeling chilled.
To help prevent and remedy this: Keep rooms warm, try to keep your Chihuahua out of drafty areas, and put clothing on your puppy or dog to see if this stops the shaking. Even just a light shirt or sweater may be enough to insulate the body and prevent shivering. n the winter, a lined vest or coat can be worn outside. When it is raining, you may find that your Chihuahua does better when protected, since a wet coat can cause a deep, penetrating cold.
Mesmo contrair-se / tremer pode ser um sintoma de convulsões em Chihuahua. Consulte este link para detalhes.
Então, para Pinky, parece ser uma representação estereotipada da raça chihuahua.