Pikachu is one of Nintendo’s amiibo that are becoming evergreen, which means the figure has been showing stable long-term sales with little seasonal fluctuation. As such, Pikachu is contributing to amiibo sales over a long period. The Pokemon icon was among the first wave of amiibo, which launched in November 2014. Link and Zelda figures based on The Legend of Zelda series are also becoming evergreen, as shown in the graph below:
Pokémon Blog 