Very judgemental, dude. Maybe he's just trying to tip over the car w/the box spring. 
But more importantly why is he wearing a skirt?
It's not a skirt; it's a kilt. He's Scottish.
Pretty sure they don't believe in labels... or physics.
Obviously, this is a metrics to imperial measurement error. Car made in Japan(?) and mattress made in USA(?).
The side profile strongly suggests it’s a female trying to fit the bed into the car,
Isn’t it possible that photo was taken in the process of moving the mattress on to, or off of, the car roof?
What’s the strap on the trunk/back bumper for?
Oops - were we actually trying to understand what was really happening?? My bad...
Its come to my notice thats its a grey/silver car thing and its a trick of vision
AT&T logo has often been called the "Death Star"
They need to think more laterally...
That explains it! 
Many purchases need to come with that kind of reminder... 
have to change pajama bottoms?
When this cartoon was published, Larson received an angry letter from the executive director of the Jane Goodall Institute about the "offensive" cartoon.
But later when Goodall (who was a fan) saw the comic, she remarked "Wow! Fantastic! Real fame at last! Fancy being in a Gary Larson cartoon!"
(ref: The Complete Far Side)
RIP Jane Goodall.