pig in the pipe
n.— «The economic impact of this glut of postwar children is familiar to those in the City, who refer to it as the “pig in the pipe”—the visible signs of the baby boomers charging through the decades.» —“The great generational robbery” by Faisal Islam New Statesman (London, United Kingdom) Mar. 5, 2007. (source: Double-Tongued Dictionary)
Further reading
If you’re madder than a peach orchard boar you’re angry indeed, or otherwise engaging in wild, unrestrained behavior similar to boars or pigs being let loose to gorge themselves on fallen fruit. Variations include crazier than a peach...
One U.S. university used the term “the pig in the python” to refer to an extra-large cohort of students. That image is not obscure. “The pig in the pipe” is, just a bit; has the more graphic form become contaminated by the term “pig” for a cylinder inserted into an oil pipeline in order to clean the walls as it passes along?