These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
This sketch has Larry Koopa complain that Bowser Jr. is the only one Bowser ever took go-kart racing. In comes Mario Kart 8, which features all the koopalings as playable racers, with Bowser Jr. nowhere in sight.
It's Been Done: Most of their observational gags have been done to death over the years.