theContratian sez: "This thread has really gone all pear-shaped."

Adj. Out of shape, unorganised, wrong. Heard in the expression go pear-shaped. E.g."All our plans went pear-shaped after our funds were cut by the finance department."

http://www.peevish.co.uk/slang/p.htm

It’s mainly a British expression. “It’s all gone pear-shaped”, one might say with head-shaking ruefulness, in reference to an activity or project that has gone badly awry or out of control.

http://www.worldwidewords.org/qa/qa-pea2.htm

If something has gone pear shaped it means it has become a disaster. It might be preparing a dinner party or arranging a meeting, any of these things can go completely pear shaped.

http://www.quad4x.net/yojinbo/slang.html

adj. If something has gone pear-shaped it means it's all gone rather wrong. Usually it's meant in a rather jovial sense, in a similar way to the American expression "out of kilter" or "off kilter". You might see it in contexts like "Well, I was supposed to have a civilised dinner with my mates but we had a few drinks and it all went a bit pear-shaped". You would not see it in contexts like "Well, she went in for the operation but the transplant organ's been rejected and the doctor says it's all gone a bit pear-shaped".

http://english2american.com/dictionary/cat_misc.html

"It went pear-shaped" is used in modern English to signify a comedic fiasco or similar disaster. In almost every circumstance, it refers to an undertaking or project that resulted in failure, but caused no grievous harm to anyone involved. Further, it provides a gentle suggestion that the fiasco was a result of nature and beyond the control of any specific individual. It is not regarded as vulgar or offensive. Despite its common usage, the origin of the phrase remains obscure.

http://alt-usage-english.org/ucle/ucle9.html

3. colloq. (chiefly Brit., orig. R.A.F. slang). to go (also turn) pear-shaped: to go (badly) wrong, to go awry.

http://www.oed.com/bbcwordhunt/pear-shaped.html