You might find it surprising, but no. Missy was not based on Mandy. However, we fully admit she looks a lot like Mandy, and knew a lot of people would notice that too. 

We needed a love rival / pest for Iris, and most of the time, when your heroïne is blonde, you get a brunette as a rival… And vice versa. 

Doesn’t matter who’s the blonde and who’s the brunette, but if you have to create a pest/rival, chances are you’ll at least try this pattern and see how it works. And, let’s be honest, most of the time it does. 

You can find it in a lots of shows… Buffy vs Cordelia (Buffy the vampire slayer), Marinette vs Chloé (Miraculous Ladybug), Clover vs Mandy (Totally Spies), Star vs Brittany (Star Vs the Forces of Evil), etc… this list can go infinitely… 

It’s just a “classic trope” here. ;)