Slim had not moved. His calm eyes followed Lennie out of the door. “Jesus,” he said. “He’s jes’ like a kid, ain’t he.”
“Sure, he’s jes like a kid. There ain’t no more harm in him than a kid neither, except he’s so strong.

– John Steinbeck

Of Mice and Men, Chapter 3. Slim and George see Lennie as a child.