Quoted By:
1. Changing effects of the love ball
>The Love Ball is more effective when catching Pokémon that are of the same gender.
GSC
This was a "bug", and was corrected in later games.
2. Attract/Captivate only work on Pokemon of the opposite gender
3. Male trainers can't wear female clothing. Female trainers can't wear male clothing.
4. Gender-locking cosplay Pikachu
5. Male Pokemon unable to produce eggs with other male Pokemon
6. Dex entries promoting heterosexuality
>Magmortar Dex Entry .
They dwell in volcanic craters. According to what is known, a single pair of male and female Magmortar lives in one volcano.