Pikachu in Pokémon Yellow: Friendship, Evolution & Pikachu’s Beach

Pokémon Yellow gives you a Level 5 Pikachu from Professor Oak in place of a normal starter. It refuses to stay in a Poké Ball, so it walks behind you, shows how it feels when you talk to it, and carries a hidden friendship value that several story events check. It also never evolves.

Type: Electric
Starts at: Lv. 5
Evolves: Never (refuses)
Catch rate: 190

Following you and showing its mood

Once you leave Oak's Lab, Pikachu follows you whenever it is in your party and has not fainted. Face it and press A to open a small window with its current expression; the face changes with its friendship and condition, and at very high friendship a heart can appear above it before the window opens.

It looks unwell when poisoned or otherwise afflicted, and it gets scared inside Pokémon Tower.
A fainted Pikachu stops following until you revive it.
In a Pokémon Center it hops onto the counter while your party is healed.
A Jigglypuff in Pewter City's Pokémon Center can put it to sleep.
Its cry is a voice clip of it saying its own name rather than the usual electronic sound.

What raises friendship

Friendship is a number from 0 to 255 shared by your original Pikachu, and gains get smaller as it climbs. Playing normally with Pikachu in your party is the best way to raise it.

Pikachu gaining a level gives one of the biggest gains: about +5 below 100, +3 from 100 to 199 and +2 above that.
Challenging a Gym Leader while Pikachu is healthy in your party adds about +3, +2 or +1 depending on how high it already is.
Walking about 255 steps with Pikachu following gives a small gain some of the time.
Teaching it a TM or HM gives about +1 until friendship is high.
Using a healing item or vitamin on Pikachu gives the same +5, +3 or +2 as a level-up.

What lowers friendship

Friendship drops when Pikachu is hurt or left behind, and the penalties grow once it is already very high.

Fainting in battle costs about 1 point, but fainting against a Pokémon 30 or more levels higher, or from poison while walking, costs about 5 (10 at the top).
Putting it in the PC costs about 3 points (5 at the top).
Trading it away costs about 10 points (20 at the top).
Revive fainted Pikachu quickly and keep it out of the PC if you want the Bulbasaur.

Checking where you stand

Several characters react to how much Pikachu likes you, so you can check without a menu.

Melanie in Cerulean City needs a friendship of 147 or more before she offers Bulbasaur.
A visitor on the second floor of the Pewter Museum comments differently once friendship reaches 101.
The older woman on the ground floor of Celadon Mansion rates it in stages, with her remark changing at 51, 101, 131, 161 and 201, and Pikachu cries out when friendship is 251 or higher.

Melanie's Bulbasaur and the other starters

The house next to the Pokémon Center in Cerulean City belongs to Melanie, who gives you a Level 10 Bulbasaur if Pikachu's friendship is at least 147. The game reads the stored value, so Pikachu does not have to be in your party, and you can only receive one. You can come back later if you are not there yet.

Charmander (Level 10) comes from a trainer at the north end of Route 24; no badge is needed.
Squirtle (Level 10) comes from Officer Jenny in Vermilion City once you have the Thunder Badge.
Neither of those gifts has a friendship check.

Why Pikachu will not evolve

Your Pikachu refuses to evolve into Raichu, so using a Thunderstone on it does nothing except show a message that it refuses, and it costs no friendship. Raichu only appears as Lt. Surge's partner. Pikachu keeps learning moves instead: Tail Whip at 6, Thunder Wave at 8, Quick Attack at 11, Double Team at 15, Slam at 20, Thunderbolt at 26, Agility at 33, Thunder at 41 and Light Screen at 50.

TM24 Thunderbolt (from Lt. Surge) and TM25 Thunder (Power Plant) are good upgrades.
It can learn HM05 Flash, but not Cut, Strength, Surf or Fly.

Early type matchups

Pikachu's Electric moves are the main reason it works well early, but they stop being useful against Ground and Rock opponents.

Brock: Geodude and Onix are Rock and Ground, so Electric attacks do nothing; use a Fighting, Water or Grass attacker.
Misty: Staryu and Starmie are Water, so ThunderShock does double damage.
Lt. Surge: Raichu resists Electric, so a Ground-type is needed.
Giovanni: Ground types are immune to Electric.
Flying birds on Routes 3 and 4 and in Blue's teams are weak to Electric.

Pikachu's Beach and the Surfing Pikachu minigame

The Summer Beach House on Route 19 holds the Surfin' Dude, who runs a surfing minigame for a Pikachu that knows Surf. Your Pikachu cannot learn Surf from an HM or TM, so on the original Game Boy cartridges the only legitimate way to get one is through a Pokémon Stadium transfer or an event. The Virtual Console re-release checks for your own Pikachu instead.

You steer Pikachu over waves and flip it with left and right to score points before it reaches the shore.
Your best score is kept, and you can view it at the printer in the beach house.
On a real Game Boy with a Game Boy Printer, you can print the score from that machine.

FAQ

Can I evolve Pikachu into Raichu in Pokémon Yellow?

Not the Pikachu Oak gives you. It refuses to evolve, and the only Raichu you meet is Lt. Surge's partner.

How do I get Melanie's Bulbasaur in Cerulean City?

Raise Pikachu's friendship to at least 147 by leveling up, challenging Gym Leaders with it healthy in your party, and not letting it faint or sit in the PC. Then speak to Melanie in the house beside the Pokémon Center.

Can Pikachu learn Surf, Cut or Strength?

No. It can learn Flash among the HMs, but a Pikachu that knows Surf can only come from a Pokémon Stadium transfer or an event, and it is only needed for the Pikachu's Beach minigame on Route 19.

Is it safe to leave Pikachu in the PC?

You can, but it costs friendship, it stops following you, and you miss the Gym friendship bonus. Keep it in your party until you have the Bulbasaur.

Sources & picture credits

Guide text is original retrogameindex writing, checked against Bulbapedia and the game data. Wild Pokémon, encounter rates, items, trainers, gifts and shops come from the pret/pokeyellow decompilation of the English game (pret/pokeyellow e89ead154b). Maps and sprites © Nintendo / Creatures / GAME FREAK, archived from the Bulbagarden Archives (listed on the image gallery).