Learn English – the meaning of the sentence, “we should not roam about in the hot sun”

Suitable replacements for "hot diggity" would be:

• gee whiz!
• gee willikers!
• oh boy!
• oh my!
• hallelujah!

The meaning is more of a retro way to express excitement or gleeful expectation. "Oh my goodness!" is similar but tends to be more of an expression of surprise than excitement.

The phrase and its ilk are not often used unless expressing excitement towards something from the era when the phrase was more common. In this case, the '60s.

"Corkscrew twists" is interesting because of "corkscrew" which refers to anything extremely curvy or twisted. A loose definition could be "something that consistently and constantly turns, twists or weaves." It is used to describe a great many, many things and can mean something that figuratively or literally twists:

This road is a corkscrew.

The dog's path corkscrewed across the lawn.

My face corkscrewed in agony.

A story's twists are its plot twists and a play that corkscrews would be one that twists a lot. The specific meaning of the quoted phrase is that the inspiring source material has a great many plot twists but the play itself is not confusing or hard to follow — the audience will not be left wondering what just happened.

wikipedia:

… in hospital when someone is ill and has to spend a lot of time in bed they can become 'bedshaped'. It sounds a bit depressing (...) but in the context of the song I wanted to suggest old age and frailty(...)

keaneshaped:

The word 'bedshaped' - I don't know if it's a made up word, but my mum's always talking about people being bedshaped, just from spending too much time being bed-ridden basically. It's quite a sad image of someone stuck there, stuck in a bed, until they become completely useless and start to lose their humanity. But just that idea of crumbling and being really frail and decrepid is something that eventually happens to everyone. That, I guess was the basis for the song in a way. So whatever happens when you're younger, even if you go off in search of glamour and ambitious and exciting things; once you get to your really old age, you've got all that side of life that just disappears.