I'm going through some villain-related videos by someone on YouTube named ColinLooksBack (that and watching workprints of the climax again, sometimes I watch them). I learned a few things I didn't know, some which might escape me now, although I'll try to remember them all. One was that apparently Pat Carroll wasn't the first choice for Morgana in the sequel any more than she was first choice for Ursula!

Apparently they wanted Anne Bancroft initially. Also, that Glut might have once been intended as a sidekick of Ursula's based on some workart. They borrowed that idea for Morgana, imo, with Undertow; there's also a specific storyboard of Ursula from the moment she cackles after finally getting thr trident for herself that you can tell they copied in Morgana's reaction when she first gets it from Melody in the cheap sequel.
Also, watching scenes of the musical's resolution of Ariel smashing the shell made me realize that M&C must have taken the idea for TP&TF's ending from what they'd seen with the musical. I enjoyed TP&TF's ending, too, except I wish Katzenberg to tell them "more Die Hard" again. I feel like the scene would've been stronger if Facilier became bigger / stronger in the moment after the illusion fades away, maybe a "fight" takes place before Tiana and Naveen finally get the necklace back from him. There was also a bit about how they initially thought of having Ursula stay in shadow her first two scenes so that we meet her when Ariel does--really glad they didn't do that.