At a guess, he found a way to steal a brick or two from someone else's LEGO kit (probably a snake, possibly Slytherin's basilisk) ... we already knew he was a childish bully after all. The fact that this would just make him even more crazy even if it did maintain his physical strength and some shred of intelligence, enough to walk, talk, and sneer at the same time anyway, actually would explain more than it calls into question.
--
"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows
--
"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows