The Hawaiian Cat Flu is a fictional disease that was created merely for the comic strip and then later used in the TV Show in the episode Garfield Goes Hawaiian.
In the Comic Strip Edit
During March 18-23, 1985, Garfield became diagnosed with the Hawaiian Cat Flu. The effects were that he starts acting like a pure Hawaiian. Such as pretending to surf, wearing a flower shirt, dancing, etc.
In the TV Show Edit
In the episode Garfield Goes Hawaiian, Garfield gets the disease. The effects however are different. Whenever he hears someone mentioning something Hawaiian he'll dance. Jon signs him up for a TV show however Garfeld gets well after secretly taking the medicine without telling Jon.
Alaskan Cat Flu Edit
This is also a fictional disease that has the same effect as the Hawaiian Cat Flu in the TV show, except the name.