Onions contain a compound which is toxic to the red blood cells of cats. The red blood cells are destroyed and this results in anemia. The specific type of anemia is called 'Heinz body anemia' because the red cells develop an abnormality called a 'Heinz body' which can be seen under the microscope.
Dug, the dog, is easily distracted by ... squirrels (well, he's easily distracted by everything, but especially squirrels). He can be talking (yeah, it's Pixar/Disney so the dog talks) & right in the middle of the sentence, he shouts, Squirrel!. Then he carries on with whatever he's talking about.
The word scaredy doesn't exist on its own. The phrase scaredy cat first appears in print in Dorothy Parker's The Waltz, published in 1933, and she's usually credited with coining the term. Thus, it is used with the word cat attached to it. Though, there has also been another cartoon titled Scaredy Squirrel, but it still isn't used for the phrase. Yes, it is used explicitly to depict someone as timid or refer to someone who is afraid/coward. I'm not sure that it is applicable to one's shyness too. Your usage of scaredy-cat in the following