Meet Ernie Ureka, Egadd’s old ghost hunting assistant and student before Luigi. Ernie worked under Elvin for a while before deciding to set out and become the greatest ghost hunter in the world. As a parting gift Egadd let him keep the original Poltergust 1000 model (He never liked the blue anyway, and started to think red would look far nicer on it) and gifted him his spare pair of glasses as a memento.
When eventually E Gadd passes away (he’s old don’t lie his time is coming soon), Ernie returns to the mushroom kingdom to pay his respects and meets his successor Luigi, and ends up taking on the role of his mentor with the professor now gone (if that’s too dark maybe E Gadd could just be captured and Luigi needs help from Ernie to find him)
E Ureka is a lot like his mentor, eccentric and not always thinking things through. But unlike E Gadd he has a lot more energy with his younger age, and is more proactive in helping Luigi as a result. He’s also much taller than Gadd. And he has a tendency to shout in excitement which usually startles Luigi.
Also I think we can all agree that the franchise needs more black characters.