Nah, even during Luke's training Yoda would hit him with a stick and act a little goofy. When Yoda came back it was during the moment that Luke was unsure about burning the Jedi tree. Yoda burns the tree down with out hesitation to remind Luke of his lesson" Do or do not there is no try." Yoda hits Luke with a stick because he forgot the lesson.I thought Yoda acting like that was an act? His stature changes when he talks to Obi Wan and he becomes less goofy. RLM brought it up and it didn't occur to me until they did. I haven't watched ESB that closely but is that not the case?