What the heck operation happens at 5:19?
vertex rip. short cut V
Thanks man.
Thanks: took a while but I figured that out. 
If the presenter could get the ScreenCast thing working, that’d be a huge help. I kinda like the “no-audio” aspect though, makes you concentrate on the screen.
press J (not F)
Up to about 12 mins, cut the fish in half as depicted, I guess to clean up the interior (?), and ran into this situation with subd on the inside:
To get to this point I deleted the back half of the interior and constructed/extruded a new set of polys to block the view thru the mouth (otherwise you’d see to the tail). I did this by selecting interior Edges and extruding them, scaled inwards, then hand-built a few polys to close off the wall. But for some reason the subdivision fails there and makes a hard corner (as illustrated). I’ve already Merged points to no effect. (Object attached)
CartoonFish_12.blend (975.1 KB)
What set of circumstances makes a subdivision surface have such a hard corner, when weights or creases have not been applied?
Face normals on the back of the mouth are flipped.