Surfing Pikachu:

Pikachu's Beach is what the little mini-game is called that can only be accessed by a Pikachu with Surf in the house directly south of the Fuchsia City PokéCenter. The Pikachu you start with cannot learn Surf so you may ask, "How the heck do I get a Surfing Pikachu?!?"

The only two ways you can do it now is by entering Nintendo Power's contest for Surfing Pikachu, or by using a game-enhancing device like Gameshark.
The third way cannot be achieved yet because it requires Pokémon Stadium. And since that hasn't been released yet, the Surfing Pikachu you can earn on that game cannot be transferred to your Gameboy.

So, cheaters, you want to know how to get a Surfing Pikachu with Gameshark? Well, before you begin messing around with your game, Gameshark codes always have the possibility to erase your game, so be careful. First for this to work you will have to sacrifice your Pikachu for the sake of playing Pikachu's Beach. The only thing that will happen is that Surf will overwrite one of your previous learned moves. Move your Pikachu to the first position and enter this code:

013973D1

If you don't want to sacrifice Pikachu then get a put a Pokémon you don't really care about changing to a Pikachu in the first slot. Then enter the following codes to get a Surfing Pikachu:

015463D1
013973D1

Now your Pikachu will have Surf and you'll be able to Surf on Pikachu's Beach!

So what is Pikachu's Beach like? Well all you do is push left or right when going over the waves to do flips in the air. If you don't wipe out when you hit the water you'll get 50 points for one flip and 150 points for more than one.

If you look in the lower right of the screenshots you'll see a HP counter, it acts like a timer and is constantly going down. Whenever you score points, the points are added to the counter, so the more flips landed the more experience your Pikachu will earn when it reaches the shore.

Once you think you've earned the highest score you can get, the Gameboy Printer will allow you to print out your score to amaze all your friends of your surfing ability! WOW.
That's about all that this mini game is. It's not much, so if you don't want to sacrifice your Pikachu you don't have to.