9. Pikablu
This was a rumour which began to spiral in the 90's when Pokemon revealed some new images in Nintendo Magazine, a tool they commonly deplored as of the huge following Pokemon had therefore making their magazine sales soar. One of these images was "Marill" but at the time, no given name had been revealed and as of its appearance striking similarities with a Pikachu (Not much, really its the mouse agenda and it being blue...), but as of this it led to create rumours of Pikachu possibly evolving or having a relation simply due to these said similarities. The community decided to put 2+2 together and decide that the new Pokemon's name was and I quote "Pikablu", attributing to its appearance with Pikachu and...being...blue. This later was quashed when Marill appeared in Pikachu's Vacation, a movie short alongside the first Pokemon Movie "Mewtwo Strikes Back" in which the little chap appeared alongside several other friend's including another new addition, Snubbull. This rumoured was so heavily though of at the time, that when the first move was released, Topps trading cards preemptively named the card for Marill "Pikablu". Goes to show how much hear-say can be thought of...