There's an exclamation point, because that's how I felt when I saw the chicken. I still kind of feel that way. The word "chicken" is just sort of fun to say--especially with tones of childish glee.
You can see that I was not raised on a farm. Nor have I had any real first-hand dealings with chickens, such as has been chronicled in the travails of
e_compass_rosa, or there would likely be a good deal less glee in my tone. Something more flat and sarcastic when pronouncing the word "chicken" would then be more appropriate, I think.