Interesting how many species weren't able to learn Sludge Bomb via TM in Gen II before Game Freak relented and decided they could in Gen III. The Bulbasaur line, Gastly line, Zubat line, Bellossom, and Octillery all initially didn't get it. Bellossom is a curious case as it's not really a Pokemon suited to "hurling unsanitary sludge" at the foe and literally drops the Poison aspect of its pre-evolution, but Poison moves are a generic Grass thing and they tend to have shitty coverage so whatever.
Even in later gens this happens once or twice. Sandygast and Sneasler are later examples of Pokemon who didn't get it at first but then later did - Sandygast apparently just to match its evolution - as are Zorua and Zoroark (Zoroark, of course, got it as an event move first).
Even in later gens this happens once or twice. Sandygast and Sneasler are later examples of Pokemon who didn't get it at first but then later did - Sandygast apparently just to match its evolution - as are Zorua and Zoroark (Zoroark, of course, got it as an event move first).