Three co-defendants charged with manipulating the stock of National Lampoon Inc. have pleaded guilty, leaving the company’s former chief executive the lone figure in the case to face trial.

The three co-defendants are Dennis Barsky, a consultant to the West Hollywood-based entertainment company; Eduardo Rodriguez, a stock promoter in New Jersey; and Tim Dougherty, a stock promoter in New York. All were charged with securities fraud and conspiracy.

Daniel Laikin, National Lampoon’s former chief executive, pleaded not guilty at his arraignment in mid-April. He is free on $50,000 bail.

Laikin’s case is being heard in federal court in Philadelphia because the Philadelphia Attorney General’s Office headed the investigation into the alleged stock manipulation. Jury selection in the trial was scheduled to begin Wednesday. If convicted, Laikin would face up to 25 years in prison.

Barsky entered his plea in late April, according to court documents. Rodriguez and Dougherty pleaded soon after their arrest in December.

The Securities and Exchange Commission alleges that Laikin and Barsky paid kickbacks of about $68,000 to the two stock promoters to inflate Lampoon’s stock price from March to June last year. Laikin and Barsky also allegedly paid kickbacks to an informant in Philadelphia who feigned interest in participating in the scheme but instead leaked information to the Securities and Exchange Commission.

Laikin’s arrest in mid-December was a setback for National Lampoon, which holds the rights to the “Animal House” and the Chevy Chase “Vacation” movie franchises. He was trying to revive the company through movie production deals, Internet ventures and a publishing arm. Most of those projects were dropped after he was arrested.

The company is now helmed by Tim Durham, a millionaire financier who knew Laikin from their days in Indiana, and is a principal shareholder.

The company’s stock was trading at about 73 cents at the time of Laikin’s arrest, down from a high of around $12 in October 1999. The stock was delisted after Laikin’s arrest.

In light of the guilty pleas, it’s likely that Laikin’s co-defendants will testify against him. Derek A Cohen, the prosecutor in the case, declined to comment. But attorneys who are not involved with the case said plea deals typically require cooperation with the prosecution.

“The usual result of someone taking a guilty plea is they are going to testify in the case,” said William Sullivan, a partner at Paul Hastings Janofsky & Walker LLP in downtown Los Angeles, who is not involved in the case. “And if you’re Laikin’s lawyers, you’re certainly going to be preparing for that event.”

Laikin’s attorney declined to comment.

The defense will likely try to cast doubt on the credibility of the co-defendants, said Mark A. Neubauer, a partner at Steptoe & Johnson LLP in Century City, who is also not involved in the case. Since the co-defendants have admitted guilt, Laikin’s attorneys will probably try to paint them as criminals whose testimony is unreliable.

Nevertheless, the plea bargains aren’t good news for Laikin.

“This certainly makes his case more difficult,” Neubauer said.