We see a two-part story about Rob's brother, Stacey (played by Jerry Van Dyke). He is a shy, timid fellow with a serious sleepwalking problem that turns him into the life of the party. Rob decides to record Stacey in somnambulance and play it back when he wakes up. Later, Rob throws a party for his coworkers (including Alan Brady), and Stacey does a brilliant comedy bit. Rob talks to him in the kitchen and discovers that Stacey was awake the whole time. He had listened to himself on the tape recorder and learned to channel the comedic energy while wide awake.
Any time Dick Van Dyke and/or Mary Tyler Moore start dancing the show turns from a sitcom into a spectacular.
The ending of "Obnoxious, Offensive," when Mel saves the day by actually getting the better of Alan for once.
A meta example: Dick Van Dyke and Henry Calvin's Laurel and Hardy impression was so good that Stan Laurel himself wrote to tell Van Dyke that it was the best one he'd ever seen.