we all know that there is going to be one episode where Frank, Dan's old partner who is always mentioned in the show about some crazy old adventure he and Dan had, finally shows up, just for one episode at the very least. I truly believe that Colin Hanks should convince his father to come and play a little cameo as Frank. Tom Hanks is only a couple years older than Bradley Whitford, plus they could make a few allusions that Frank was almost exactly like Jack when he first started out, and we all know that will give Jack a scare, seeing as all of those stories Dan tells are not like the kind of cop Jack wants to be. Plus a couple characters can state how they look similar, like Frank may be the first, but Dan and Jack don't see it, but Liz may see it, and maybe even Lt. Ana will see it as well and mention something like "oh dear god, I've created something worse than just having two Dan Starks, I've recreated Frank" or something like that, i realize that line sucks but you get the picture, this could elude to the fact that maybe if Frank was like Jack in the beginning that maybe he changed before Dan or something. I don't know, its just something, but i seriously do think that Tom Hanks should play Frank, just in one episode though. because we know that eventually Frank will appear on screen at some point in time.