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.
YMMV: Happy Wheels
Alternate Character Interpretation: Some of the more creative user-made levels, including one where the Wheelchair guy is just one of several clones, and one where the Irresponsible Dad is smaller than a mouse.
Complacent Gaming Syndrome: For some reason, a lot of levels are made for the Segway Guy. This could be justified, as most levels require someone to be standing upright, especially with games that have you throw stuff.
Crosses the Line Twice: You'd think general dismemberment of handicapped elders, children (and one toddler), and even Santa Claus would be nothing but horribly outrageous, but this game manages to go so far with it that it becomes hilarious.
Game Breaker: Though it takes practice, it is possible to fly using the Wheelchair Guy's rocket. Needless to say, this makes clearing most levels very easy.
The Irresponsible Dad can do it too, to some extent. Mashing the lean keys will have him glide for as long as you can keep it up.
Beating the "It Keeps Happening" level is ridiculously easy if you're playing as Pogostick Man. Just jump upwards and the finish line is right there.
Helicopter Man can straight up fly, and therefore has maneuverability incomparable to other characters.
Ensemble Darkhorse: Irresponsible Dad is without a doubt the most popular of the current characters, likely due to being a favorite of many of the Let's Players who have taken a shot at the game.
Good Bad Bug: Though some of said bugs fall into this category.
Nightmare Fuel: A rather major case of YMMV, as to some people all of the death and dismemberment in the game can come off as more disturbing than funny.
Some of the user-made levels can also contain plenty of nightmarish content, such as the ones made by user "kirbypwnage" (especially his "Haunted Mansion" levels).