In Mother 3
Happy Boxes are first seen in Chapter 3, advertised by Salsa under the control of Fassad. Happy Boxes are implied to be brainwashing devices, hypnotizing people to buy consumer goods from New Pork City, and also leading to the modernization of Tazmily Village. The villagers in Tazmily Village were skeptical at first, and only three were sold, to Abbot and Abbey, Biff, and Isaac, respectively. Three years later in Chapter 4, it is shown that nearly everyone in the village owns a Happy Box, excluding a select few. Lightning often strikes the homes of anyone who does not own a Happy Box, namely Flint's family, Alec, and Reggie.
Despite their similar appearance to televisions, they are not actually displaying anything, and they were redesigned multiple times to make them less resemble televisions.
"It is said that just by putting one of these suspicious-looking boxes in the corner of a room, one can achieve happiness. By Fassad's demand, Salsa was forced to distribute them."
- Nindori.com interview with Shigesato Itoi, translated