It's not an uncommon strategy. It's done with Level 1 Rattata, Raticate, Clefable, Cleffa or Clefairy. I'm sure there are others too. Actually he's pretty dumb for using Rattata, who can die to Sandstorm/Hail or have its sash broken by entry hazards. The Clefairy line is immune to all that, thanks to Magic Guard - it even prevents death from Poison or Burn.