The Walt Disney Co. added Spider-Man, Iron Man and the X-Men to its vast cast of characters yesterday with a surprise agreement to buy Marvel Entertainment Inc. for some $4 billion.

"Adding Marvel to Disney's unique portfolio of brands provides significant opportunities for long-term growth and value creation," Disney president and chief executive officer Robert Iger said. "We are pleased to bring this talent and these great assets to Disney."

Disney and Marvel, in a joint statement, said that Marvel shareholders would receive a total of $30 per share in cash plus approximately 0.745 Disney shares for each Marvel share they own.

It said that based on the closing price of Disney stock on Friday, the transaction value is $50 per Marvel share or approximately $4 billion. Shares of Marvel soared 26.08 per cent in New York to $48.73 about an hour after the market opened.

Disney shares were trading 2.05 per cent lower at $26.29.

The deal, which caught analysts and the market by surprise, was announced shortly before the opening bell on Wall Street.

Besides Spider-Man, Iron Man and the X-Men, Marvel's cast of over 5,000 characters includes Captain America, the Fantastic Four and Thor. Marvel chief executive officer Ike Perlmutter said Disney is "the perfect home for Marvel's fantastic library of characters given its proven ability to expand content creation and licensing businesses