Film director Steven Spielberg lost his cool on his recent movie 'The War Horse' because real horses are not good actors.

The famous stage play, which uses life-size theatrical puppets has been running since 2007, but when comparing its 'cast' to the movie, it has a different set of rules. When Spielberg got down to working with horses, he felt their acting abilities didn't match up to their wooden adversaries, which are visually more appealing and have a bigger effect on audiences.

Puppet horses are made to be very expressive, but when using animals in movies, it's hard, if not, impossible to direct them on how to act. In fact, this could be the subject of a few video spoofs yet to come.

Using animals as main characters in a film is considered the hardest kind of directing there is requiring trained personnel to be on set at all times. This also goes for young children who must be given extensive resting hours along with the care of a guardian on the shoot.

Check the first teaser released this past week:

War Horse Teaser preview

Steven Spielberg has directed some of the most inspiring films of the past few decades, and 'War Hose' is hotly anticipated. The movie stars Emily Watson, Tom Hiddleston, Jeremy Irvine and David Thewlis. It will be released on 28th December.