Susan Cherry is shown in this undated photo.

Paging Steve Carell! Having immortalized "The Forty-Year-Old Virgin," perhaps he could do the same for that newest of new office dwellers: The Fifty-Year-Old Intern.

Interns eligible for Social Security are becoming an increasingly common presence in the workforce, taking unpaid slots once filled by teenagers or newly minted college graduates.

The Fiscal Times wrote about 53-year-old Susan Cherry, who returned to school for medical-lab work then found that she'd have to do an internship to meet her degree requirements.

It used to be unheard of for senior people to accept junior jobs-let alone unpaid ones. But a 2009 report by CareerBuilder found that among laid off workers aged 55 and older, 63 percent said they had applied for jobs more junior than the one they'd lost. In the same report, 25 percent of employers surveyed said they had received applications for entry level jobs from workers aged 50 and older. Eleven percent said they had gotten applications from retirees.

Some of these aged newbies are workers called out of retirement by boredom or financial need. Ryan Hunt, a senior career advisor at CareerBuilder.com, says it's that latter force that's driving the job hunts of many seniors that he sees. Other mature workers are looking to transition to a new career.

In either case, experts say, older workers are increasingly willing to take unpaid internships as a way to gain a foothold. And some employers are happy hire to hire them-not just because they work cheap, but because they bring with them mature judgement and valuable experience.

In a 2011 study by CareerBuilder, 75 percent of employers said they were willing to consider hiring over-qualified candidates.

Oldsters' gains, to some extent, are coming at youngsters' expense. As recently as 2000, only 13 percent of workers were 55 or older. Now, according to the Bureau of Labor Statistics, that same percentage is expected to hit 25.2 by 2020. In the past 12 months, older workers got more than 67 percent of the new jobs being created.

Youngsters aren't unaware of this generational competition, and experts say that the mix of young and old in the same office can make for inter-generation conflict. Marci Alboher, vice president of Civic Ventures, a nonprofit that studies Baby Boomers in the workplace, says it's the employer's responsibility to minimize such tensions while, at the same time, to take advantage of the different assets that young and old each bring to work.