In that interview, Milligan mentioned that the only voice he did that he based on someone else was the one for Eccles, the quintessential Goon. He said it was based on Edgar Bergan's wonderful Mortimer Snerd, who is probably my favorite all ventriloquist dummies.
Many of you may not know Eccles, so I thought I'd post an excerpt of him here. This is the famous "What Time Is It, Eccles?" sketch between the genial but utterly dimwitted Eccles and Bluebottle, a little boy. Making this all the more fun is that Bluebottle was voiced by the third member of the Goons, Peter Sellers.
Needless-to-say, the clip here and the animated were all added later. The best of of listening to The Goon Show is in your imagine, which in this case means turning away from your computer monitor. But it's certainly fine either way. More to the point, as you will hear, the Goons took the concept of surreal to its utter extreme. Yet 60 years later, it remains a hoot.