Hiya, I'm not completely sure it's a bug but I have reasons that suggest it might be.
According to Wiki, the requirements are you are OT and Pikachu is the starter.

I've played this game for the first time two years ago now roughly, so I don't really remember what I took.
However, I have no other Kanto starter registered in my Pokedex, which suggests the fourth option - Pikachu.
And both Pikachus I tried teaching Surf are OT mine.

 

On the other side I don't have the Pikachu/thunder ball  on either of them(again,per a Wiki page).
One of them does have a different image, although I again don't know why.

 

Please help x)

Hey there @Nilante

 

Surf can be taught via a Move Tutor called Victor in Route 19 for the price of 8,000.

However, he will only teach it to the Pikachu if you are the OT (Original Trainer) of that Pokemon.

 

I believe they removed the requirement that it required you to choose it as your starter.

 

You can read more about the move tutor on the wiki here.

Read more about Victor in Route 19 here.

 

Reason it might have failed:

If you tried to teach it using the HM03 Surf found in the bag, then that might be the reason it failed, as teaching Pikachu is exclusive to Victor in Route 19.

In other words, it can only be learned by paying a Move Tutor for teaching a Pokemon a specific move.

 

If you still cannot teach it Surf from Victor, please let us know below.

So that a staff can forward this bug to the right people.

 

Hope this solved your problem.

If not, let's hope it will be resolved in the near future.

Edited March 22, 20215 yr by Electrocute4u

Oh shoot, I'm so sorry. I somehow missed that!
You were correct in your assumption, I was using HM03 Surf.
It works with Victor, thank you!

1 minute ago, Nilante said:

Oh shoot, I'm so sorry. I somehow missed that!
You were correct in your assumption, I was using HM03 Surf.
It works with Victor, thank you!

 

Glad to hear that!

I'll try to reword the wiki page, so that people would not run into the same problem you had.

 

Enjoy surfing along the waves with your Pikachu!