 In May 1821 , Grimaldi collapsed after a performance of Undine ; or , the Spirit of the Waters . Doctors diagnosed him as suffering from " premature old age " . JS took over his father 's role and completed the remainder of the show 's run . Now acting as an official understudy , JS filled many of his father 's other theatrical engagements , including a rerun of Harlequin and Mother Bunch ; or , the Yellow Dwarf , in which he caused a scandal by threatening and verbally abusing a heckler in the audience . In the early 1820s , Grimaldi made a brief recovery and held a six @-@ week engagement at the Coburg Theatre where he appeared as Clown in Salmagundi ; or , the Clown 's Dish of All Sorts ; a pantomime which ran for a week before being replaced by Disputes in China ; or , Harlequin and the Hong Merchants . Both productions were successful , but Grimaldi was taken ill half way through the latter 's run . 
