Seems to be coming down to a custom new operator and dynamic memory handling.
in character.cpp, right above the constructor
MACRO_ALLOC_POOL_ID_IMPL(CCharacter, MAX_CLIENTS)
in entity.h
#define MACRO_ALLOC_POOL_ID_IMPL(POOLTYPE, PoolSize) \
static char ms_PoolData##POOLTYPE[PoolSize][sizeof(POOLTYPE)] = {{0}}; \
static int ms_PoolUsed##POOLTYPE[PoolSize] = {0}; \
void *POOLTYPE::operator new(size_t Size, int id) \
{ \
dbg_assert(sizeof(POOLTYPE) == Size, "size error"); \
dbg_assert(!ms_PoolUsed##POOLTYPE[id], "already used"); \
/*dbg_msg("pool", "++ %s %d", #POOLTYPE, id);*/ \
ms_PoolUsed##POOLTYPE[id] = 1; \
mem_zero(ms_PoolData##POOLTYPE[id], Size); \
return ms_PoolData##POOLTYPE[id]; \
} \