A Happy Box is an item that appears in Mother 3. These mysterious boxes are manufactured by the Pigmask Army (as shown by the presence of their insignia), and are used as a mean of corrupting the residents of Tazmily Village into supporting the infrastructure the Pigmask Army introduces to the islands.
Flint is among the few residents of Tazmily who does not eventually accept a Happy Box; this results in his home being a frequent site for lightning strikes, which the villagers see as an omen. In reality the damage is caused deliberately by the Pigmask Army's own Thunder Tower to frighten others into accepting Happy Boxes and make an example of those who resist.
Though they are similar in appearance to televisions or desktop computer monitors, director Shigesato Itoi has maintained that Happy Boxes are neither televisions nor monitors, explaining that they "aren't even displaying anything" and could even be fish tanks.