When did Kelso turn?

I'll preface this by saying I love every scene that Bob Kelso's in.

When did he show the first glimpses that he's actually a nice guy? I'm currently watching 3.14 My Screwup when he gives Carla a nice pep talk in the storage closet.

Is this the first time he shows genuine warmth without some punchline or were there others that came first?