Plan B

Plan B.
1.
A fallback plan in case the original goes wrong. Usually instituted after:-

• The death of the friendly contact on the Libyan border.
• The death of a fellow spy/dignitary at the hands of the friendly contact on the Libyan border.
• Annihilation the the brand spanking new, dog's bollocks SUV made especially for extracting yourself from messy situations like this.

Plan B is usually actioned when not expected to be needed and as a result, often made up 'on the fly'. In the age old tradition of things, it would not be a proper Plan B if it had been planned in advance.

See also:
Lose with a little panache

2.
The name of a "morning after pill" (levonorgestrel), which is available on prescription. --Oolong

Having a back-up plan shows sound strategic thinking and is only to be applauded.

But with me and my group of friends Plan-B has always been to go to the pub and get pissed....

Stage one of your plan for world domination gone down the pan, and the fluffy white cat jumped out of the window? Plan B works everytime.
Aim to settle down and have kids before you're thirty; not happened? Plan B will see you on the road...
Plan to get up at 8:00 am for a whole year to go to your computer science course; too costly to implement? Again Plan B never fails
Plan to get a serious alcohol dependency problem? Ah well, perhaps Plan B should be refined to 'stay in the pub for ever'