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.
Ear Worm: Seriously. It's a good thing for parents that the songs are as fun as they are...
Ensemble Darkhorse: Austin, whose popularity with the viewers (especially the Periphery Demographic) is, strangely, in direct counterpoint to how often he appears on the show. It may or may not be a coincidence that the much cuddlier Pablo, Tyrone and Uniqua appear in nearly every episode and on most of the marketing.
Germans Love David Hasselhoff: The series is so popular in Latin America that it's easier to find fansites and videos of the show in Spanish than the original English.
Growing the Beard: From the second season onwards, the animation was much improved, and the music became even better.
Nightmare Retardant: "Scared of You" is based around this trope. The episode features a skeptical Austin meeting Tyrone (as The Mummy King), Uniqua (as a rather cute werewolf), and Pablo (as a vampire), all of whom are far more scared of each other. It ends with all five of the kids having a big monster dance party.
Periphery Demographic: Because those songs are damn catchy. Also, the animation is beautiful and the writing is smart and funny.
The Untwist: Frequent, in the course of finding ways around their inability to actually hurt or arrest anyone. During "Whodunit?", for instance, it turns out that Tyrone was the thief, but he didn't really steal the jewels; Tasha gave them to him. It was all a plot by Tasha to liven up a rainy day.
The Woobie: If you think about it, all five of them are. Each character has a moment of Woobie-ness but Austin is the biggest contender, especially in "Race Around the World" where he keeps losing the race.