Are there cases where a double horizontal stabilizer is useful? I was watching Agents of Shield recently, and in it the team fly a plane that's claimed to be a modified C-17 Globemaster. It has two extra engines, rotary turrets, and, according to the wiki, a pair of half-length wings at the rear of the fuselage, seen here:

(image courtesy of Agents of SHIELD wiki)

To me, it also kind of looks like a second horizontal stabilizer. Certainly some of the modifications to this fictional plane are pure flights of fancy, but is there any basis behind this one? Is there any reason why this feature would be useful? Have there possibly been any experimental or production aircraft with something like this? Or is this pure "cool factor," with no real basis in aviation?
The main aerodynamic purpose of the horizontal stab (or certain canards) is to provide longitudinal stability. 

If the rear wing with the 5th and 6th engine flies "up," like the main wing, then it will counteract the longitudinal stability of the horizontal stabilizer. If the rear wing flies down, like the h-stab, then it is just extraneous, since the h-stab can be made as large as necessary.

If all you want to do is to add extra engines, they can be mounted on the main wing, like in the eight-engine B-52 bomber:



or the six-engine Antonov An-225 cargo jet: