Battle · Lt. Surge (Vermilion Gym)
Beating Lt. Surge
One Raichu at level 28 - but first you have to get through the door.
medium
In Yellow, Surge has exactly one Pokemon. That does not make him easy: Raichu at L28 is fast and hits hard.
Solve the trash cans
Two switches are hidden in the gym's trash cans. Find the first, then the second must be in an adjacent can - get it wrong and both re-randomise.
Go next door to Diglett's Cave
The cave between Route 2 and Route 11 is full of Diglett, with the occasional Dugtrio. Ground is immune to Electric.
Teach it Dig
TM28 Dig comes from the Rocket in the burgled Cerulean house. Dig is 2x on Raichu and Diglett takes nothing back.
Fight
Lead the Diglett or Dugtrio, use Dig, done. Reward: Thunder Badge (+12.5% Speed, Fly usable) and TM24 Thunderbolt.
Collect your Squirtle
Officer Jenny in Vermilion hands over a free level 10 Squirtle once you hold the Thunder Badge - your third and last free starter.
Do not teach TM24 to your Pikachu: it learns Thunderbolt for free at level 26.