Book Dumb: Heavy technically should have failed his driver's test, considering he answered that you should "crash into the thingy and die" when approaching an oncoming train. Yet because he answered the extra credit question correctly, he passed.
He also answered "all of the above" on the previous question which asked what is the minimum safe distance to park from a fire hydrant (the other choices being 25 ft, 50 ft, 98 miles away, and "what was the question?")
Cheaters Never Prosper: If you had to extract a moral from Heavy Takes His Driving Test, this would be it. A few of the classes try to use their unique weapons and abilities (i.e. the RED Engineer programming the car to do all of the test for him, the RED Demoman placing sticky bombs in specific locations to move the test along, etc.) The entire RED team fails their tests for these reasons. RED Spy almost passes it perfectly, had he not stopped the car to get out and kill the pedestrian.
Also, in Heavy Goes Bowling, the RED Heavy does this repeatedly, even going as far as to lie in the middle of the lane so that BLU Heavy can't knock down the pins. The BLU Heavy eventually wins after RED Heavy is finally disqualified for trying to shoot him.
In "Heavy Goes Bowling", Francis gets killed by G-Man, yet shows up later on to drive his motorcycle through the bowling alley and eventually slam his drink on the counter hard enough to shake the entire bowling alley and knock down the last bowling pins, winning the game for BLU Heavy. Also, when Francis is killed by G-Man, the HUD says that Louis was killed by the Fast Headcrab Zombies, yet he survives and makes his way back inside the bowling alley only to be hit in the face by a bowling pin and attacked by Fast Headcrab Zombies again.
In "Heavy Takes his Driving Test", most of the RED mercenaries die during their driving tests, yet show up alive at the end of the video so BLU Scout can tell them that they failed.
In "Heavy's Retarded Holiday", Heavy's companions (Ellis, Frank, Chuck, Ezio, a random rebel) are quickly killed by a giant monster cat with a disintegration ray, yet inexplicably show up alive to celebrate after Heavy defeats said monster. Additionally Heavy and Ellis have a number of experiences that should be lethal but at best momentarily incapacitate them, including several falls of insane heights and Ellis being shot several times by two sentry guns.
In "French Toast" Heavy foolishly touches a hot frying pan (after specifically being told not to do so) and instantly burst into flames (with a note labelled "death" to ensure the audience did not attempt this), but he's perfectly alright in the very next shot. Beforehand he also tastes his incomplete French Toast mixture ends up dead of salmonella, complete with same.
Freeze-Frame Bonus: While the RED Heavy is shooting after he gets defeated in 'Heavy Goes Bowling', look at the onomatopoeia in the last gunshot.
Flying Car: Somehow, a derpy-eyed RED Scout causes his car to soar through the air.
MacGuffin Melee: Several characters (though none as much as the Heavy) will use any means of violence to get the Crit Sandvich in "The Quest for the Ultimate Sandvich".
Mood Whiplash: In "Heavy's Retarded Holiday", Heavy ends up in a tense situation where he is hanging over a high ledge by one hand, calling for help. Ellis is slowly reaching out, trying to help him and just as he takes his hand:
Ellis: Oh my God, it's Christmas!
Cut to a shot in which a Christmas tree and presents are visible in the distance.
Heavy: Come sing with me!
Heavy grabs Ellis and jumps off the ledge as he starts singing.
Running Gag: Heavy Goes Bowling has at least three instances involving a character being thrown outside the bowling alley and flying into a car, setting off its alarm in the process. Two of them, both of them involving Louis, end with the victim being viciously mauled by Fast Headcrab Zombies. The third time, the scene cuts away as soon as the car alarm begins, as though the video is saying, "Yeah, you already know what's about to happen."
Shout-Out: In addition to all the videogame cameos, Dr. Hax appears in "Heavy Goes Bowling" and even helps BLU Heavy during his bowling match against RED Heavy.
Sophisticated as Hell: "A mixture of ingredients do not own the proper attributes to be mentally impaired, dumbass"
Stuff Blowing Up: "Heavy Takes His Driving Test". Several things go up in mushroom clouds when they're so much as tapped.
Surreal Humour: Especially in "Heavy's Retarded Holiday", where the Heavy ends up in a strange place resembling an enormous bedroom in which people appear and disappear out of nowhere, get killed in absurd ways and inexplicably turn up okay later, a giant monster cat goes on a rampage after being disturbed fro its sleep by Heavy, Ellis, Frank West and Chuck Greene, and Christmas happens spontaneously.
Verbal Tic: Heavy's "Uh." sound when he's uncertain of something.
Wacky Racing: Technically not a race, but the driving course would certainly qualify, considering it featured dangerous jumps, an oncoming train, and a civilian trying to cross the street. Then of course most of the RED team takes it further with various absurd methods that result in disaster.
The Wonderland: Although the universe in this series is already this, it is certainly more coherent than the dream world Heavy enters in "Heavy's Retarded Holiday".