Greg Berlanti is the one guy who I can imagine in the most recent of years to be the living and breathing depiction of Scrooge McDuck jumping off of a diving board into a pool of money. You see, he is solely responsible (to my knowledge anyway) for every single DC show you are seeing now, hearing of or have seen in recent years.
In 2012, the show Arrow starring Stephen Amell played the DC character Green Arrow. Fans and critics alike deemed the show to be a Batman "Rip-off", not rip-off per-say but, his enemies were Batman's enemies. That didn't stop the show as the show was great and improved by each season. I believe it was season 2 where they introduced Barry Allen whom would later become The Flash, to then have his own series a year later, introducing crossovers from each show and then expanding the now aptly titled 'Arrowverse (Arrow universe) wider to include lot of other heroes and different teams throughout DC history. Supergirl, Legends of Tomorrow, Black Lightning, Batwoman and the up and coming Superman & Lois, not to mention other DC shows he helps to produce, Titans, Doom Patrol and Stargirl. Even when you watch the Chillin Adventures of Sabrina, Greg's name is there! But without him and his input and efforts, Stargirl may not have been made and be as good as it is.
I'm not sure which year Stargirl takes place, whether before the Arrowverse characters as I'm assuming, techinically, it is meant to be as Stargirl is part of the Justice Society of America which comes before the Justice League of America, but the JSA have been wiped out by the villains. The villains win and the sole survivor, Stripesy meets and marrys a lady named Barbara, Courtney's mother and they move to a town called Blue Valley and he leaves his past behind him. Unfortunately, Courtney stumbles across the Cosmic Staff, previously held by Starman and would ONLY work for Starman, Courtney, now Stargirl wants to pick up where Starman left off and try to uncover a plot of villainy.
The cosmic staff is essentially its own character. If you are into Marvel movies and know about Thor's trusty hammer, the cosmic staff is similar to that in the sense that only the user can use it, but the staff is sentient. The staff moves by itself, helps the user to fly, flashes a bright light and can be used as a formidable weapon in combat. The way the staff moves with and around Stargirl helping her whilst she is wielding the staff is nothing like i've ever seen before. The staff does however come across as very convenient to plot and story though. When they want to have the staff work for the story or move/act in a particular way, it would. If they don't want it to work in a particular way and they want to show Courtney get hurt or whatever, then it won't. There were times I felt like the Staff could have assisted Courtney in moments and it did nothing.