There was a brief glimpse - and sadly only from the side - of Chris Pennock as Mitch Williams on tonight's 20/20 special,
General Hospital: The Real Soap Dish:
Though honestly I was more excited to see a glimpse of vintage Tracy Quartermaine and Daddy than I was in seeing Mitch because I never much cared for his character. But then, we weren't suppose to.
And if you never actually saw Pennock on GH, here's a YouTube clip:
General Hospital: 1980: Tracy Quartermaine & Mitch Williams