Awesome Music: All of it. Each of the team's themes from World Race were loved by many. Shirako from Acceleracers was loved due to his music, among other things.
Narm Charm: Yeah, it's about a bunch of guys who take driving way too seriously, but a lot of people love it nonetheless.
What Do You Mean, It's for Kids?: The series has shown violence plenty of times. World Race had one driver, Kurt Wylde, actively trying to sabotage and almost kill the others. It doesn't stop in Acceleracers either. It has been implied by the look of Banjee's wrecked car in the Swamp Realm that he didn't make it. The same could be said for other drivers from World Race. Not only that, but in Ultimate Race you can see Markie and Kurt fight with Kadeem, unable to change his ways or even help him in the slightest. Think the Power of Friendship prevails here? Not in that fight at least. And it's always possible that Kadeem might've not survived. What's known for sure though is that another drone, Gelorum, got thrown to her apparent death by an Acceleron. Maybe teaching all this violence to kids isn't the best idea.
In the Storm Realm Monkey urges Markie to go back to save Taro because the Metal Maniacs are "welded".
Similarly, Tork goes to fight the drones for the same reason.
Monkey tries to cheer up Pork Chop after they go through the Water Realm.
Nolo says that he only hates one of the Metal Maniacs, not all of them.
In the Metro Realm Tork goes back to see Nolo is alright after Nolo turns his car upside down. This is despite everything Nolo has done to Tork.
All except one of the drivers go to save Markie from the drones after he got lost in the Junk Realm.True Companions.
Instead of becoming a Acceleron Vert goes back to fight for his friends.
Ensemble Darkhorse: The more attractive drivers are pretty well-liked. Such as Vert, Markie, Kurt, and Shirako.
Fridge Horror: In the Storm Realm Markie consider scraping Monkey's car seat off of his car so that the car seat doesn't slow his car down. He was planning to leave one of his own team in the Storm Realm. And, as seen with Kadeem we know what happens to people who get lost. They die because they get stuck in the realms forever or they get turned into drones. Markie didn't know this but still...
When Tork and Nolo and testing the Accelechargers for the first time in Speed of Silence where are they driving? Why, where they were driving, was part of the track missing? There's no way they could've built an entire track just to test the Swamp Realm Accelecharger.
When Pork Chop's name is called for the Water Realm who does he punch his fists out to? He punches towards the camera but I'm pretty sure no one's there...
Nightmare Fuel: The realms are fun and cool to drive in-Then various things will pop out and try to murder you, like giant flesh eating slugs and insects, kamikaze trucks, lightning bolts, Monster fish, sharp curves that you can fly off from into something that can kill you, Giant scorpions, giant buzzards, radioactive wastedumps, giant alligators caverns with giant bats and mountain sized stalagmites, bottomless pits, quicksand, black holes, extreme solar flares-and even if you survive all of that, if you don't make it out of each of the realms within an hour, you're trapped forever. Drive to survive, indeed...
Kadeem and Markie both being slowly converted into Racing Drones. Markie was lucky enough to escape before he underwent full conversion, but still came out permanently altered for life. You can tell Gelorum evidently turned Markie's left arm robotic to prove she wasn't screwing around when she was threatening him, but Kadeem... Poor Kadeem... And all the creepy smiles and twitching he makes afterwards proves something is VERY wrong and messed up inside him now.
Sidetracked by the Gold Saucer: The Realms prevent drivers from doing this by only being open for one hour. Otherwise, what's stopping history-buff drivers from exploring the Ruins Realm? Or mechanics from pirating from the Junk Realm? The Water Realm would solve all of the droughts world-wide if it could be accessed at will. The Metro Realm has the same issue. On top of that, the Neon Pipeline Realm is pretty cool to drive in. And the Space Realm is a veritable joy for astrophysicists... when black holes aren't afoot, that is.
Some Anvils Need to Be Dropped: Two very clear ones involving the Rivarly between Tork and Nolo and Markie and Kurt involving how bad revenge is: Nolo refused to listen to his fellow drivers about how his brother Tone wasn't killed by Tork and clung onto his rivalry with him to the point where in the Swamp Realm, their rivalry almost killed them and most of their teammates. In Wyldes case, he keep his grudge against his brother for abandoning him in Prison to the point where he tried harming Kurt and his other friends and enemies multiple time and wound up captured and tortured by the Drone. The second is that anyone can change for the better as seen with the Wyldes relationship when Kurt rescued his Brother and the two fought the Brainwashed and Crazy Kadeem and lead to the two reconciling with one another.
Too Good to Last: Come on, this movie series made it to Toonami, one of the biggest bastions of action cartoons and anime, a niche demographic for this sort of thing that gave this line of movies its cult following and was the place it first debuted. For it to sputter out like the way it did has nothing to do with ratings- it is because the production company responsible ran out of funding to make any more movies.