This has been proved time and time again in the anime such as in the episode "Where No Togepi has Gone Before" and "Snivy Plays Hard to Catch" when he got infatuated bởi a wild Togepi's and Ash's Snivy's Attracts respectively, and both those Pokemon were female. Also, if bạn go on Bulbapeida and go to the page about Ash's Pikachu it will say Gender: Male. Here's a picture of what a female Pikachu looks like. This is a picture from SS027 of Ayumi and her Pikachu. There used to be a video of this episode on YouTube with English subtitles, unfortunately the video got taken down because the account of the person who made the video is no longer active.
This is true. It was proved ever since the episode where Ash, Pikachu, and the rest of the male co. dressed as females and Pikachu was also included in this so Pikachu was proved to be a definite male there.