Well, we got to see his interactions with his father in at least one episode, numerous instances of him with other Janitors to screw with JD, and of course his marriage to Lady. So far, all we know about these security guards is that they're security guards, and they work various other jobs on/around the campus. Not that it didn't take a long time to develop the Janitor's character, but there was certainly more to him than simple gags to screw with JD, it was a very intriguing personality. OH! and his stuffed squirrels collection too.
Edit: I guess what I'm mainly getting at is the whole process of going from a completely developed show and transitioning to a new cast. It's like starting all over again, basically. You have to watch them grow as characters again.
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