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.
That One Achievement: Trials HD's Marathon. You have to play through the Ultimate Endurance tournament, which consists of twenty courses, without faulting once. The tournament is completely compromised of levels that aren't any harder than Medium difficulty, but one false move and it's back to square one.