might have done
 【问】 He might have realized that you were pulling his leg.
 请说明句子里might have realized的含义。
 【答】 这是个歧义句。
 A. might+完成体不定式有时用来表示埋怨或训斥(埋怨对方本应该做的事而没有做)，这个结构在语义上相当于should+完成体不定式或ought to+完成体不定式，可以译为“本应该”(If you tell someone that they might have done something，you are telling in an angry waythat they ought to have done it.)：
 1. You might have let me know before! (Mansfield)
 你本应该在以前让我知道!
 2. But I think you might have told us half an hour ago. (Shaw)
 但是我认为你本该在半小时前告诉我们。
 3. You might have warned me she was coming. (CGEL)
 你本应该通知我她要来的。
 按照这种理解，你提问的句子的意思是：
 他本该明白你是在跟他开玩笑。(He ought to have realized that you were pulling his leg. )
 B.情态动词might+完成体不定式表示(从现在的观点看来)“可能已发生了某事”(If you
 say that something might have happened，you mean that it is possible that it happened. )
 1. He might well have said that. (EED)
 他很可能说过这样的话。
 2. I might have come to a wrong conclusion. (Priestley)
 我可能得出了错误的结论。
 按照这种分析，你提问的句子的意思是：
 他可能已经明白了你是在跟他开玩笑。
 (might have done的其他含义见may have done)