For the interior, I made the same cookie/cake combo as in John's cake. The recipes are here. I covered the base in red homemade fondant. Man, does the red food color stain hands! Then I used a bowl to form a Rice Krispy treat and recruited John for carving and art direction. Alex wanted the cake to look like this bohrok, but I forgo the brown fondant on top and rolled out a piece of my homemade dairy-free caramel for the top decoration. I brushed on luster dust with a cotton puff to make the head silver and the caramel decoration bronze. It was my first time using luster dust dry on fondant and it got a little messy. I ended up lightly dusting the red base with dust as well. I liked the effect and it made the impressions on the bottom trim stand out more. If you look closely at the base of the cake, I pressed a clean piece of Bionicle Lego into the fresh fondant trim to make a pattern. If I did it again, I would have pressed Lego pieces all over the base fondant for a cool pattern. I need another reason to make a fondant covered cake so I can play with impressions and luster dust! But, I'm hoping Alex picks something a lot easier for next years cake. Something square...maybe Spongebob...
Here's the birthday boy with his cake: