A Murray cameo! He ruled hardcore in MI3 and his appearance, though brief, in MI4 was much appreciated. I'm really hoping to see him even for a moment in one of the episodes.
That said, there were so, so many hidden in-jokes for fans of the Homestar universe packed into SBCG4AP, and my favourite character Homsar had some really incredible segments, especially in episode 2.
I'm sure they're sailor-tailoring these games around everything people have said they wanted in the next Monkey Island adventure, I wouldn't be surprised to see the old "harbinger of doom" return.
And whatever happened to Largo LaGrande, besides the april fool's "MI5" joke a few years back?