Monster Stat #3:  the animated metal egg
  (from Adventurers #79)

frequency             Unique
# appearing           1
climate/terrain       any
movement              12", assuming it doesn't trip
armor class           -5
HD                    50 hp
thac0                 11
# of attacks          2
damage/attack         1-2/1-2
special attacks       none
special defenses      none
magic resistance      none
intelligence          Non-
alignment             Neutral
size                  S (1')

  This construct was found by the Adventurers, within the Underdark.
A perfect ovoid, it was shiny silver in color, and weighed about a
hundred pounds.  Its "skin" was composed of a hard metal of some
kind, and proved extraordinarily resistant to damage.  At random
times, the egg sprouted skinny arms and legs, at which point it
tended to run about blindly.  A chime of opening proved sufficient
to force the egg's limbs to appear.
  Whether or not the thing had any sensory capabilities remains a
mystery.  Though it could have mounted an attack with its frail
little arms, the egg never really tried to hurt anybody.