Unemployment
Unemployment is one of the major themes in Cardboard by Doug TenNapel. Without a job, a parent struggles to meet his family's needs. In most circumstances, children ask for toys and birthday gifts. However, if the parent is unemployed, it becomes difficult to satisfy the family's needs. In the novel, Cardboard, Cam's father, Mike, is unemployed. When Cam asks for the birthday gift, Mike struggles to look for what he can afford and uses all his savings to buy cardboard, which he uses to make a box for his son. Mike's struggles reflect what many poor parents go through in life, especially when they try to meet the needs of their children.
Bullying
Bullying is another important theme that emerges in the novel Cardboard. The novel explores Cam's life and shows how rich kids bully disadvantaged children. Rich kids can access all the expensive toys they need in life, which makes them think they are superior to poor kids. For instance, Marcus is a rich kid who bullies other kids like Cam because they cannot afford what his parents buy him. Making matters worse, Marcus believes that because he is rich, he can take anything from poor children to add to his collection of toys. When Marcus discovers Cam has cardboard, he steals it to create monsters.
Grief
Losing a loved one leaves permanent pain to the remaining family members. If the dead person played a significant role in the family while alive, no one can fill her gap. When Cam's mother dies, his father, Mike, is left with the burden of raising him without adequate finances. Cam's mother used to work and support her family wholeheartedly. The grief and pain continue to pull Mike backward because he finds it hard to move on. Cam also misses his mother and does not understand why death is so cruel to children when it takes their mothers forever.