Arnie is a mentally handicapped squirrel in a parody of What's Eating Gilbert Grape in "Irregarding Steve". His brother Gilbert has to watch after him and his morbidly obese mother until she dies. When their tree is set on fire by lighting, Arnie and Gilbert hit the road on the back of a bus.
Arnie appears in a cameo in "Office Spaceman" in Roger's photographs of himself.
Arnie is voiced by Johnny Galecki.