When Rick first tells Morty he fixed portal travel, the creature that appears out of the portal is the creature which appears at the end of the opening titles.
When Rick talks about his aversion to fixing the portal gun, the show is really referencing the writers and their thoughts on plot moving episodes.
Rick tumbles down the asteroid crater as Homer Simpson did in an early The Simpsons called "Bart The Daredevil". Homer reprised this just before this episode airing called "Lisa the Boy Scout".