I voted for Haggis McMutton, but I would also love to see Edward.
However, an element which should come back in my opinion is 'Pappapisshu'. (Yes, this is how it is written.) This made me laugh every time in CoMI, as it was not used too often, but was still used enough times. (It would have been good, though, if at the end, when Lechuck hits Guybrush time after time, he wouldn't only say 'youch'.)
I was really happy to see it again in the Rise of the Pirate God, but I would have liked to see it some more times.