"Make' Em Laugh" is a song first featured in the 1952 film Singin' in the Rain, frenetically performed by Donald O'Connor. Written by Nacio Herb Brown and Arthur Freed, the song is closely based on Cole Porter's "Be a Clown". It finished at # 49 in AFI's 100 Years ... 100 Songs survey of top tunes in American cinema.

Who sang make em laugh in singin in the rain? Okie... think carefully first, then make a decision:
To answer the question, consider the following: "Make' Em Laugh" is a song first featured in the 1952 film Singin' in the Rain, frenetically performed by Donald O'Connor. So, the answer is Donald O'Connor.