the only one laughing at his own joke 
(ROOT (NP (NP (DT the) (JJ only) (NN one)) (VP (VBG laughing) (PP (IN at) (NP (PRP$ his) (JJ own) (NN joke))))))
(ROOT (NP (NP (DT ) (JJ ) (NN )) (VP (VBG ) (PP (IN ) (NP (PRP$ ) (JJ ) (NN ))))))