Complex sentence: The character of Beaker was introduced in season two; during the first season Bunsen hosted Muppet Labs by himself, but the writers soon realized that another character was necessary to show Bunsen's failings.
Split into simpler sentences: The character of Beaker was introduced in season two. During the first season Bunsen hosted Muppet Labs by himself, but the writers soon realized that another character was necessary to show Bunsen's failings.