The employees crushed the boxes because they were empty.

Who is "they" in this prior sentence?
the boxes
Kathy looked after the children of Mrs. Faith since she wanted to have a night out at town.

Who is "she" in this prior sentence?
Mrs. Faith
Planet Express was bought out by Mom's Friendly Delivery Service so they can eliminate the competition.

Who is "they" in this prior sentence?
Mom's Friendly Delivery Service