My cat is shaking, eyes twitching, not eating. What's wrong with him?

Poor Pippy! Yes, it certainly sounds like she's sick - shaking is often a sign of pain or discomfort in cats, and not eating or drinking is also a very non-specific sign of illness. Unfortunately, these are very vague symptoms that could be caused by almost anything, so it would be best to have Pippy examined by a vet as soon as you are able to. He/she can do a thorough exam to check for any areas where she might be painful, and can also do blood work and x-rays if needed to help determine the problem.

Tell your mom to take him into a vet first thing in the morning, this does not sound normal and needs to be checked out asap. There could be something stuck in his mouth, he could have a severe dental problem, or a bad ear infection.

You need to take Robin into a vet immediately, it's a medical emergency he won't eat. If cats go long enough without eating, they will develop a fatty liver which is fatal without treatment. He could have a systemic illness, infection, inflammation, or injury causing his symptoms. Please take him into a vet now.

This sign is very concerning and may eventually be in a life threatening condition. Fever or extreme discomfort may be present. I would strongly recommend an immediate check up to confirm this clinical suspicion and have the appropriate treatment performed. Antibiotics may be needed.

This is probably unrelated to the flea treatment, it could be an infection that Bobby is suffering from. If by tomorrow the symptoms do not improve I strongly recommend taking him back to the vet to get treated.

I suspect Cleo is not feeling well and may be nauseous. Just like people, there are many conditions that can make pets feel sick. This could range from bacterial over growth to intestinal blockage. Also like us, diseases are best addressed early and this may result in a better prognosis. You need to monitor Cleo closely. If she is not eating or drinking well for 24 hours, if there is vomiting/diarrhea/coughing or signs of pain, I recommend to have her examined by the veterinarian today. If the lethargy lasts for 24 hours, your kitty also needs to be examined. The doctor will need to learn the underlying cause in order to give appropriate treatment. Bring in a stool sample in case the doctor needs to test it. At home, Cleo should continue resting. Encourage eating and drinking. Bring her the food and water. Fluid intake is very important when pets and people don't feel good. You may try offering her some boiled white meat chicken or canned tuna (in water not oil). Hopefully this will pass quickly. I hope Cleo starts feeling better quickly! Please feel free to post any additional questions.

All of those signs are very concerning that something more serious is going on. If Theo hasn't eaten at all in two days and can't keep anything down, it is best to seek care from your vet or another vet ASAP as this can indicate more severe illness or underlying issue. More thorough workup such as bloodwork or X-rays are also a good idea to try and find the cause such as an infection, virus, obstruction, etc that could be causing the underlying issue.