[Other] How to make sprites appear after an event?

[NightwingJay]

I see this in the Saffron City map where some sprites aren't shown. And I assume they appear after you take down Giovanni and the Rocket Sprites go away and normal ones stay. I checked the header and it really doesn't make any sense to me. (Btw Saffron has 2 maps for some reason in A-Map)
But anyways if that has nothing to do with the title. How do I make sprite appear after you (for example) beat a Gym Leader (I assume my flag will be the badge you earn) and have some sprites waiting for you outside?

 

[esperance]

Making a sprite appear is quite similar to how you can make a sprite disappear via flags. At some point before the player will reach the map, you hide the event with a flag. When you're ready for the event to appear, you simply clear that flag. You can do this process of setting and clearing the flag as many times as you like.

In Saffron City, you'll notice that the events that show up once Team Rocket has been beaten all share the same flag. This flag is cleared when you talk to Giovanni in Silph Co., alongside the setting of the flag that hides the Team Rocket grunts throughout the city.