When Jon pulls out the strand of Christmas lights from the box of decorations, you can clearly see the whole strand. Not only does it have 6 or 7 lights on it, but there are no plugs on it, either!
Actually, that's a misinterpretation of one of the episode's jokes. The episode takes place in July, yet the newscaster announces that, while the mayor has declared it to be July, a meeting of City Council has voted it to be August.
One man says its july but the newscaster says its august
Jon: (After seeing Garfield in winter clothes) Garfield, you can't just make it winter in the middle of sum... summ... this is not a bad idea. You're trying to think cool.
Garfield: You catch on fast.
Jon: This is great. What else can we do to make it more wintery around here?
Garfield: (after blowing into his hands) This way!
(They head to the garage: Garfeild points to the box of Christmas decorations)
Jon: That's box, but that's where I store the Christmas decorations.
Garfield: Come on, let's deck the hall and Fa la la. You know, the la la la.
Jon: Well, why not.
(They place Christmas decorations around their home.)
Jon: This was a great idea, Garfield. I don't feel half as warm now.
Hubert: Dear, you know Arbuckle across the street?
Woman: The one with the cat that eats everything?
Hubert: That's the one.