GSC kind of had something like a Pikaclone it was Marill or mostly known before gen 2 as Pikablue.
Marill had similarities to Pikachu, but it wasn't a true Pikaclone in the same sense as Plusle/Minun, Pachirisu, Emolga, and Dedenne. For one, it was Water type, not Electric, and it also actually evolved into something. Marill also didn't have little circles on its cheeks like all the Pikaclones.
I think Marill, along with Togepi, was more meant to be an addition to the "cute, fairy-esque" line of Pokémon, which also included Pikachu itself, as well as Clefairy and Jigglypuff.
Pikachu, Clefairy, and Jigglypuff were all small, cute Pokémon who were extremely rare in the games (despite being otherwise heavily promoted outside of the games) and evolved with stones. They also all received baby forms in Gen 2, which all evolved via happiness.
Marill pretty much fit the same mold as those three. It was small and cute and heavily promoted, yet was also extremely rare in the games. Surprisingly, though, it wasn't a stone evolver. Marill also received a baby form in the generation after it was introduced, and like Pichu/Cleffa/Igglybuff, Azurill also evolved via high friendship.
Similar story with Togepi. Small and cute, heavily promoted, and rare in the games. And, by Gen 4, it was also a three stage line with a baby form that evolved via happiness and a middle form that evolved with a stone.
