Exciting, stylish, fun, entertaining, action packed, and very, very impressive. Trollhunters is an adventure story of kid-turned-hero à la Buffy the Vampire Slayer; it has a light, quirky, and humorous attitude à la Meet the Robinsons; incredibly detailed and immersive world-building à la Avatar; and a good dose of Del Toro's sinister monsters and dark psychological twists. Although aimed at a younger audience, it holds the depth and complexity of any adult show, while remaining whimsically childlike. Light and dark are perfectly balanced – it's got both silly kid humour and suspenseful situations that are genuinely unsettling. This is, after all, the same guy who made Pan's Labyrinth, and you can definitely see the influence here.
I was constantly impressed with the depth of imagination and real cleverness of this series. The unique monsters, magical elements, and new plot complications never stopped coming. The overall story arc is fantastically well-written, and character developments and relationships are truly believable and affecting. The baddies are interestingly conflicted, the goodies are endearing and extremely likable. You've got the terrified yet courageous hero Jim, clumsy yet smart wing man Toby, and sweet yet kick-ass Shakespeare-aficionado Claire, and all the rest, equally original. Brilliant voice acting too, especially from the late Anton Yelchin. Oh, and it's beautifully animated. Little wonder it won six Emmys!
Del Toro's creation is flawless. Trollhunters is something you can enjoyably binge-watch and then put off watching the last few episodes because you don't want it to come to an end. I can't wait for the second season – I haven't watched anything this good in a long time.