Complex sentence: Then SpongeBob says that his treatment is working and then calls Sandy and tells her not to come, but a little while later, Sandy arrives and Patrick says that SpongeBob is fine and doesn't need to go to the doctor.
Split into simpler sentences: Then SpongeBob says that his treatment is working and then calls Sandy and tell her not to come. But a little while later, Sandy arrives and Patrick says that SpongeBob is fine and doesn't need to go to the doctor.