The Maneki Neko, or "Beckoning Cat", is a good luck charm intended to increase the owner's wealth and can be found across Japan and China. As such, it also makes several appearances in Japanese video games, often providing a similar benefit.
The Pokémon Meowth is derived from the Maneki Neko, having a coin on its head and moves like Payday, which provides the player with additional Pokédollars. In the Goemon games, Maneki Nekos will provide various benefits if found; for instance, in The Legend of Mystical Ninja for the SNES, a grey Maneki Neko will upgrade Goemon's and Ebisumaru's weapons while a rare golden Maneki Neko will refill their health and increase its maximum capacity.
In many cases, the Maneki Neko is simply background dressing and does nothing. Due to their ubiquity in Japan, it provides a bit of realism for Japanese players to see them in games as well.