The pressure just got stronger for Bob Iger to carve up Disney

• Activist investor Nelson Peltz has reportedly upped his stake in Disney.
• This means pressure is on for CEO Bob Iger to turn the company's stock around.

The pressure knob for Bob Iger just got turned a little higher.

Like in any classic Disney movie, a would-be antagonist is back with a plan. In this case, that comes in the form of CEO Iger's own personal antagonist, activist investor Nelson Peltz.

Peltz, who runs hedge fund Trian Fund Management, has been upping his stake in Disney for months. He now has a holding of about 30 million shares, worth more than $2.5 billion, and is expected to ask for multiple board seats, The Wall Street Journal reported late Sunday.

It's the sequel to the billionaire Peltz's first proxy fight against the House of Mouse, which ended in February after Disney agreed to cutting costs and laying off about 7,000 of its employees.

"We wish the very best to Bob, this management team, and the board," Peltz said on CNBC at the time. "We will be watching. We will be rooting."

If he has, indeed, been watching, he probably hasn't loved what he's seen. Since Disney's stock price peaked for the year in February at about $113 per share, it's fallen more than 25% to about $84 per share.

So what could Peltz want this time?

Trian declined to comment, and Peltz hasn't discussed a specific plan, but if he's following his typical playbook — stripping away declining assets and a focus on profit, profit, profit — it will likely mean a call for breaking up Disney.

ABC and Disney's other linear networks, like FX and The Disney Channel, could be among the first to go. While Iger once considered the news network to be Disney's crown jewel, he's been apparently floating the idea of Disney selling ABC since the Sun Valley conference earlier this year, when he let it slip that they "may not be core."

ESPN, too, could be spun off: While Iger has been hesitant to say anything about selling the sports network, there's no doubt it's an attractive asset for buyers — particularly a tech company, like Apple.

"It checks every box. And they want live sports content — that would be a massive growth engine," Wedbush Securities analyst Dan Ives told Insider last month. "I believe it's a matter of not if, but when, Apple buys ESPN." Apple hasn't commented on the speculation and didn't respond to a request for comment for this story.

If a break up happens, what's left will be Disney's film studios, parks, and streaming — the three businesses Iger has said "will drive the greatest growth and value creation over the next five years."

For a shareholder like Peltz, the goal of these moves would be to improve the stock price and make sure Disney follows through on a plan to pay dividends.

And at least some analysts think a possible break up is a good move: "When a stock is under pressure as Disney has been, it needs to unload core assets and conserve capital," media M&A advisor Peter Csathy told Insider last month.

Disney didn't respond to Insider's request for comment.