Complex sentence: One of the students dresses as a ghost in order to frighten Stan and Ollie and while they are sat on a bench the ghost's hand comes through the hedge to help Stan smoke his pipe and cigar.
Split into simpler sentences: One of the students dresses as a ghost in order to frighten Stan and Ollie. Whilst they are sat on a bench the ghost's hand comes through the hedge and helps Stan to smoke his pipe and cigar.