A recent biography of Alec Guinness says that he did not think too much of this film. He felt it was a rehash of characters he played before like in The Lavendar Hill Mob or The Man In The White Suit. Why he took it is a mystery unless this was the best he was being offered at the time. One thing he did note to his wife Merulla was that he felt that Robert Redford was going to be a big star.
Situation Hopeless...But Not Serious is one weird film. It has some interesting and funny moments in it, but it's just way too weird.
Guinness is some quiet and nebbish like German who in the waning days of World War II when two American fliers Captain Robert Redford and Sergeant Michael Connors take refuge in his basement, he locks them up there and they become his own private prisoners. Not that he treats them bad, he just craves company since he has no friends. On V.E. Day had he let them go, no harm no foul. But Guinness keeps them on through 1946.
I could probably draw a lot of conclusions as to why Guinness's character was so wanting their company, but the Code was still somewhat in place. And as Guinness was a repressed gay Catholic man his whole life, this film must have hit close to home.
For the strangest Alec Guinness film out there, check out this one.