The Tv icon was the star of beloved 1950s variety programme Your Show of Shows, performing alongside Reiner and acting out sketches co-written by Brooks, and now his colleagues are mourning his loss.
In a statement issued to The Hollywood Reporter, Reiner writes, "Inarguably he was the greatest single monologist and skit comedian we ever had. Television owes him a debt of gratitude for his pioneering work and the great shows he gave us all. Render onto Caesar what is his due. He deserves real applause from the American people."
Brooks adds, "Sid Caesar was a giant - maybe the best comedian who ever practiced the trade. And I was privileged to be one of his writers and one of his friends."
And Allen, who worked with Caesar on a number of his Tv specials in the late 1950s, states, "He was one of the truly great comedians of my time, and one of the finest privileges I've had in my entire career was that I was able to work for him."
Newsman Larry King and actors Whoopi Goldberg and Arnold Schwarzenegger were among the first to remember the late star on Twitter.com, and now Marlee Matlin has added her comments, writing, "RIP Sid Caesar. A long and illustrious life, heaven must've needed some laughs and called up this pioneer and first gentleman of comedy", while director Jon Favreau adds, "RIP Sid Caesar. A pioneer and a genius."
It's also long, long, long... well, you get the picture. Mad, Mad World is...