Steinbeck first tells us about their physicality. Lennie is large and George is small. Lennie begins talking and we can tell he is simple or mentally challenged. George takes on a parental roll with Lennie. Lennie clearly cannot remember or process tasks that need to be performed and George has to take care of him,
The little man jerked down the brim of his hat and scowled over at Lennie. "So you forgot that awready, did you? I gotta tell you again, do I? Jesus Christ, you're a crazy bastard!" "I forgot," Lennie said softly. "I tried not to forget. Honest to God I did, George."