Complex sentence: Truly and the baby ponies are delighted when they wake to find Dream Valley covered in snow, and set about building a snowpony, undeterred by Galaxy's warnings that it shouldn't be snowing in summer.
Split into simpler sentences: Truly and the baby ponies are delighted when they wake to find Dream Valley covered in snow. They set about building a snowpony, undeterred by Galaxy's warnings that it shouldn't be snowing in summer.