A "pantomime horse" is a phrase used to describe two people, one behind the other, who pretend to be a horse by wearing a costume together. Full definition
On TV, we see Shirley Temple dancing in The Little Colonel (1935) and Betty Grable sashaying with a costumed pantomime horse in Coney Island (1943).» (metroactive.com)
Following them are tractors full of smoking gypsies, foresters hauling logs, spearmen tossing their ribbon covered spears in the air and a troupe of pantomime horses, known as Rusa. (thetravelmagazine.net)
The only interesting pitch in recent years, from someone hoping to become the rear portion of this particular pantomime horse, came from Jon Cruddas when he went for the job back in 2007. (labour-uncut.co.uk)