'He thinks it's a mirror': Internet howls with laughter at video of Trump stroking a horse's rear end
President Donald Trump strokes a horse's rear end (Screen cap).

President Donald Trump on Monday greeted the horse-drawn carriage that brought the official White House Christmas Tree to 1600 Pennsylvania Avenue -- and he found himself getting better acquainted with one of the horses at the front.

After shaking hands with the two men who were steering the carriage to the White House, the president approached one of the horses and gave it a few strokes on the rear end with his right hand, as shown in the GIF below posted by Vox's Aaron Rupar.

The video of Trump rubbing the horse's rear drew immediate howls of laughter from all across Twitter -- check out some of the best reactions below.