Elon Musk and Larry Ellison, tech giants now vying for the world's richest title, made surprising cameos in the 2010 film Iron Man 2. Musk's persona even inspired Tony Stark's character, while Ellison was humorously dubbed the "Oracle of Oracle.

The jump came after shares in Oracle, which make up a significant part of Ellison's fortune, soared more than 40%, boosted by the database software company's surprisingly rosy outlook for its cloud i...