>>31263356Most people probably played through gen IV without ever finding a Munchlax because of the arbitrary way you were supposed to find it, and BW2 gives it to you as a trade that's only possible in the summer. That's the only two games where you can get Munchlax in ways other than breeding Snorlax with an incense (excluding it as a gift pokemon in S/M), so it's definitely not the only Pokémon where that's true.
For Happiny and Bonsly it probably is true (although gen II gives you Sudowoodo pretty early, right after Whitney), but is there anyone who ever really wanted to use Chingling/Chimecho or Mime Jr./Mr. Mime early in the game? I can't imagine these Pokémon having significant fanbases.