Washington (CNN) -- There's nothing funny about the issue of migrant farm labor -- unless Comedy Central's Stephen Colbert is discussing it.

Colbert, accompanied by a media swarm, sarcastically testified on Capitol Hill Friday about the conditions facing America's undocumented farm workers. The popular host of "The Colbert Report" told members of a House Judiciary subcommittee that he hoped to bring attention to the workers' hardships.

"I certainly hope that my star power can bump this hearing all the way up to C-SPAN 1," he joked.

"America's farms are presently far too dependent on immigrant labor to pick our fruits and vegetables," he told the subcommittee, keeping in character with the arch-conservative he plays on television.

"Now, the obvious answer is for all of us to stop eating fruits and vegetables. And if you look at the recent obesity statistics, many Americans have already started."

Colbert told the panel that "we all know there is a long tradition of great nations importing foreign workers to do their farm work."

"After all," he said, "it was the ancient Israelites who built the first food pyramids. But this is America. I don't want a tomato picked by a Mexican. I want it picked by an American, then sliced by a Guatemalan, and served by a Venezuelan in a spa where a Chilean gives me a Brazilian."

"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants," he declared. "He did it because he killed a man back in Ireland. That's the rumor."

Colbert appeared before Congress the day after "The Colbert Report" showed video of him packing corn and picking beans on a farm as part of a challenge from a pro-immigrant-labor group.

"I'll admit I started my work day with preconceived notions of migrant labor," Colbert said. "But after working with these men and women ... side by side in the unforgiving sun I have to say -- and I do mean this sincerely -- please don't make me do this again. It is really, really hard."

The brief experience, he said, "gave me some small understanding why so few Americans are clamoring to begin an exciting career as seasonal migrant field workers."

Colbert appeared alongside, among others, United Farm Workers President Arturo Rodriguez, whose group over the summer launched "Take Our Jobs," a campaign that challenged U.S. citizens to replace immigrants in farm work.

The group, which says only seven citizens or legal residents have taken it up on the offer, argues that immigrant workers aren't taking citizens' jobs, and is pushing for a bill that would give undocumented farm workers currently in the United States the right to earn legal status.

On his show Thursday night, Colbert mocked those deriding his appearance before the committee, saying he agreed that showing up in character would "sully the good name of experts that Republican-controlled Congresses have actually called to testify in the past," like Elmo, the Sesame Street character who promoted music education before a House subcommittee in 2002.

Republicans on the subcommittee were not impressed or swayed by Colbert's appearance.

"Maybe we should be spending less time watching Comedy Central and more time considering all the real jobs that are out there -- ones that require real hard labor and ones that don't involve sitting behind a desk," said Rep. Steve King, R-Iowa.

"If we did we'd realize that every day ... Americans perform the dirtiest, most difficult, most dangerous (jobs) that can be thrown at them."

Many of these workers, King said, "would prefer the aroma of fresh dirt to that of the sewage of American elitists who disparage them even as they flush."

"It's an insult to me to hear that Americans won't do this work," he added, arguing that the hiring of undocumented workers is driving down wages and taking jobs away from those in the country legally.

Rep. Lamar Smith, R-Texas, used the occasion to rip the Obama administration's immigration policy. The notion that there's little competition for jobs between citizens and undocumented workers is a "myth," he claimed.

"We could make millions of jobs available to American citizens ... if the federal government simply enforced our immigration laws," Smith asserted. "Unfortunately this administration is turning its back on American workers."

Democrats were quick to challenge the Republicans' claims.

While Americans will take tough jobs, "study after study" shows that "people would rather have no income and no welfare than take the back-breaking jobs that the migrant farm worker has to do every single day," said Rep. Howard Berman, D-California.

"Were it not for immigrant farm workers in this country, there would be no seasonal fresh fruit and vegetables," he said.

Most of the media attention, however, remained focused on Colbert. The chairwoman of the subcommittee, Rep. Zoe Lofrgen, D-California, told CNN's Dana Bash before the hearing that she didn't think Colbert's appearance was a stunt.

"Celebrities add pizzazz to an issue," she said. "I hope his celebrity will bring attention" to this one.

But another Democrat, Michigan Rep. John Conyers, initially seemed unimpressed with Colbert, asking him to leave the committee room and merely submit his written statement instead.

Colbert noted that he was testifying at Lofgren's invitation, and said that he would remove himself at her request.

Conyers later told CNN he feared Colbert would create a "circus" atmosphere. But Colbert, who engaged in a question-and-answer session with the subcommittee, actually turned out to be "profound," he said.

CNN's Jason Hanna, Deirdre Walsh, Alison Harding and Catherine Shoichet contributed to this report