The Big Dog carries four backpacks. Looks like two guys in a robot suit.
Second picture: The Big Dog keeps running along into the shadow.
Closeup of the rear legs--no guys in the suits after all.
Some big meany kicks the Big Dog...but the Big Dog cleverly sticks his leg out and recovers anyway.
The Big Dog walks up hill; through snow; over rocks.
Closeup of the gasoline-powered engine; back on leash in the lab.