https://www.cbr.com/stargirl-season-4-titans-beast-boy-crossover/

Stargirl creator Geoff Johns reveals Ryan Potter's Beast Boy from Titans could have appeared in Season 4 had The CW series not been canceled.

Stargirl Season 4 Would Have Crossed Over With Titans For a Major Multiverse Story (https://www.cbr.com/stargirl-season-4-multiverse-crossover/)

Stargirl's Brec Bassinger reveals that there were plans for Season 4 to crossover with other DCTV shows like Titans and The Flash.