Improvisation actor Del Close who appears as 'Hobo Wearing Eyepatch' would later play a much larger role as 'Reverend Meeker' in the 1988 remake of 'The Blob'.
In an interview in Fangoria magazine, screenwriter Anthony Harris stated that a good portion of the filmed material was improvised on the set and that the script was ignored.
In spite of having a stunt person on set, Robert Walker Jr. lobbied director Larry Hagman to do his own stunts for the rope climbing sequence in the finale. Walker had an acrobatic background, and was allowed to do the stunts.
Harris felt "Beware! The Blob" was too "funny" and not "scary enough" to be successful.
The enormous success of The Blob (1958) led producer Jack H. Harris to try to do a sequel. Richard Clair had already written a script titled "A Chip Off the Old Blob," but the project had been shelved for many years. In late-1970, Harris' son, Anthony Harris, who had just graduated from USC and was working with a music publishing company, expressed interest in working with his father. Looking for a project, they both agreed on the "Blob" sequel. Larry Hagman, who owned the beach house next door to Harris, mentioned that he had never seen the original The Blob (1958). Harris showed Hagman his personal 16mm print of the film, and he showed such interest, Hagman told Harris he would be able to assemble his friends for the cast, as he felt everyone wanted to be "Blobbed"... but only on the condition he would direct the picture.