 At first , the production company planned to use snakes in latex suits for the worms ; when this proved impossible , mealworm larvae were used . The effect of the worms crawling in the host bodies was achieved with wires under fake skins , including a skin with hair for the dog . Digital effects were used for scenes involving the worms swimming in jars and entering the dog 's ear . Although extra footage of the worm scenes was shot so they would last as long as intended if Fox 's standards @-@ and @-@ practices officials asked for cuts , no edits were requested . " Ice " was the first significant role in the series for makeup effects artist Toby Lindala , who become its chief makeup artist . The dog used in the episode was a parent of Duchovny 's dog , Blue . Ken Kirzinger , who played one of the scientists killed in the episode 's cold open , was the series ' stunt coordinator . 
