Honestly, while Tim Robbins is a big guy, I never once though, "He should be smaller to be able to do that stuff." Just for me: When a story doesn't have my complete attention, that's when my mind can wander into I'm Not Buying That Part land. The first four times I saw Star Wars in 1977, not that it made an impact, was a great example of glaring story blemishes and silliness being subsumed by the enjoyment of the tale. Shawshank, the same thing. I snapped at the offering, hook, line, and sinker, and got reeled in, gasping at the end, going, "Okay, that was worth it." In reading about the movie, if one believes Wikipedia, Rob Reiner had wanted to direct the movie, casting Tom Cruise as Andy and Harrison Ford as Red. Mr. Cruise has the short and wiry build that could more easily fit through a prison tunnel and sewer, but I am doggoned glad that the movie didn't go that route.