Your rival,and his real name is Silver.
Silver first appears in the Generation II games, lurking outside of Professor Elm's lab, looking through the window. When talked to, he will deny everything and push the player away. During the player's journey to Mr. Pokémon's house, Silver makes his move, stealing one of Elm's two remaining starter Pokémon.
So for example,I chose Cyndaquil,your rival chooses your weakness (in this case,it would be Totodile),and Lyra(if you chose boy),or Ethan(if you chose girl),would have Marill.
Ethan (if you chose girl)
Lyra. (if you chose boy)