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.
Canon Defilement: At this point, with so little to go on, and the series having so little characters, it's hard to avoid. Generally, as long you don't completely break all the rules of canon, you'll come out okay (for instance, Martin suddenly taking a level in jerkass for no reason besides the author wanted to will probably not be well received. However, if it's due to a Despair Event Horizon, that would be different). This is largely due to all the Canon Fodder lying about.
Come for the X, Stay for the Y: Fans of their other 4 series came for the Kratt Brothers, but stayed for the awesome. (Note: Most fans came from Zoboomafoo, half the number of Zoboo fans are Kratt's Creatures, and we've yet to hear of anyone from Be The Creature or Be The Creature 2.)
Ensemble Darkhorse: Aviva. Doesn't help that she's showcased about 75% more than any other character (including the villains). Arguably, Zach- he's the favorite subject of Fan Fiction.
Even Better Sequel: Technically, triquel- Be the Creature was followed by Be the Creature 2. Hardly anyone remembers these, yet Wild Kratts is a remake of them.
Foe Yay: There has been fan speculation of Zach and Aviva having been in a relationship at one point, and let's just say that she remembers things about him that no one else would remember about someone they purport to dislike. Also, in "Mystery of the Weird-Looking Walrus", she knew the code to disable the skullcaps without being told- either Zach is that much of a moron/creature of habit that he'd use the same code knowing his opponents knew it as well and could disable his systems before he knew anything, or else she knows him a lot better than she's putting on.
Food Porn: You may feel a sudden craving for brownies after watching A Bat in the Brownies
Fridge Horror: In "Flight of the Draco", Donita Donata uses a "Pose Beam" device to freeze Martin in place and manipulate him to walk a runway as her unwilling model. That in itself is pretty creepy when you think about it, but it gets worse. The scene cuts away for a minute after Martin is first caught in the beam, and then it reveals him in the outfit Donita plans to make him model. In other words, he was stripped while paralyzed. The fact that Donita seems a little too into him definitely doesn't help...
Genius Bonus / Shout-Out: Chris' "Have flippers, will travel" from "Polar Bears Don't Dance" is a paraphrasing of the sci-fi book "Have Spacesuit, Will Travel".
Also, Martin's dialogue line of "Have noseplug, will travel." in the episode "Skunked!"
Growing the Beard: If the episodes are in at least semi-correct order, the show does this in season 2 (started with Ker-Honk). If they're in some kind of reverse order, then the show has gotten worse (although by a negligible margin).
The Zach-Bots, especially when they take the form of a human.
Many of the cruel things Zach does to the animals he captures, such as brainwashing walruses so they are forced to stay underwater until they drown just so they can find a pearl he stole.
Gourmand's teeth gnashing in Stuck on Sharks. What made it even more creepy was he was talking to himself while he was doing it.
Seven from Octopus Wildkratticus, post suit-tangling…
Donita Donata paralyzes animals to make living jewelry out of, and even did it to Martin (to use as a model), on whom she seems to have a crush. There can be consequences to this: At least in humans, when the body is paralyzed with the brain intact (which is different from medical paralysis or coma), the victim usually strokes out within 3 months.
Gourmand talks to himself in an unjustifiable way, sings jingles about eating endangered animals to himself; heck, the whole thing about cooking and eating endangered animals is creepy enough.
Periphery Demographic: The show has a small but thriving community of older fans who remember the Kratt Brothers' earlier shows fondly.
Squick: The Kratts are a little too fascinated with worm slime in "Mystery of the Squirmy Wormy".