I must say that everything in this icon screams cute. From Luka's position, to even the artists style. I have seen many Luka and Tako Luka images but I haven't found one of them in pixels before. Thus making this one of all of your pixel icons my favourite! An adorable little icon pixel piece if ever I saw one.
The amount of detail put into this little gem is excellent! The tones in the hair especially impress me. I love the way you have shown the darker shaded area, without the colour becoming "dirty looking". That is a definite skill you have!
Keep up improving your work!