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—The Pixelblocks slogan.
Pixelblocks is an obscure, discontinued construction toy. Essentially, they're like Legos, only they come in only one size and shape of brick, which can be attached together in all three dimensions. The principle behind Pixelblocks is that you can assemble these uniform pieces into any form imaginable, just as a television screen can display any image using millions of differently colored pixels.
Consequently, one of the common applications of Pixelblocks is to make sprites of classic video game characters. For example, if you wanted to make a model of Sonic the Hedgehog to hang up on your wall, you could buy enough blue and white Pixelblocks and make it yourself. Or, if you wanted to customize your Sonic, maybe make him yellow with a Pikachu tail...
Basically, Pixelblocks are another way for Chris to crowbar his fantasies into reality, just like drawing shitty comics, homemade Yu-Gi-Oh! cards, customizable video games like LittleBigPlanet and Animal Crossing, and so on. Until holodecks are invented, the only way Chris can hang out with Sonichu in real life is to build him, and Pixelblocks provide a way to do that.
It's worth noting that Chris, having no idea that Pixelblocks can even function in the third dimension, never made 3D sculptures with them. And frustratingly enough, he is capable of using Lego to build 3D structures.
Most of Chris's Pixelblock creations were probably lost in the house fire, but photographic evidence shows that at least Chris's self-portrait survived.
Stuff Chris has built from Pixelblocks
While a full survey of Chris's bedroom is difficult at best, one can spot a few Pixelblock constructs hanging on the walls in his YouTube videos. Among them:
A substitute of Chris, who appears to be sporting an Afro.
The Heart Torch of Fail.
Sonichu and Rosechu, with Sonic looking on.
Sprites of Mario, Link and Samus. What's sad is they look better than anything Chris can draw.
Pixelblock Chris, having survived the fire. Note that this image is featured on the Pixelblocks website.
Pixelblocks in Sonichu
Pixelblocks appeared twice in Sonichu 4. According to Chris's own diary entries, he would play with them at Wal-Mart, so this may be why he used them in the comics adapting his confrontations with the Manajerks there.
In Sub-Episode 5, the Ancient leader of the Cherokee Clan revealed that Chris could use his Sonichu Medallion to imbue special powers to the Heart Torch, a Pixelblock model he had constructed. Chris followed his advice, and used the empowered Heart Torch to summon his dream sibling, who helped him defeat the W-M-Manajerk.