Back in 2014, Hasbro was ranked as the third largest toy maker in the world, with estimated annual sales of $4 billion. The only two companies ahead of them are LEGO in second place with $4.5 billion in estimated annual sales, and Mattel in first place with $6.3 billion in estimated annual sales.
However it seems that Hasbro could be leapfrogging LEGO to become the largest toy maker in the world, because according to a report from The Wall Street Journal (via Engadget), Hasbro has reportedly made a takeover bid for Mattel. Unfortunately details about the deal are scarce, such as how much Hasbro offered for Mattel, and whether or not Mattel is interested in the offer, and unsurprisingly neither company has offered to comment on the rumor.
It has been pointed out that in a way this takeover makes sense for both companies, and that they actually complement each other. Hasbro has stopped manufacturing their own toys and ditched their manufacturing facilities, while Mattel still has theirs, which means that Hasbro taking over Mattel would see Hasbro being able to take advantage of that fact.
That being said, there is also some concerns about how regulators will react to the potential takeover as it could violate US antitrust law, similar to how regulators were opposed to the idea of AT&T and T-Mobile merging, and Sprint and T-Mobile merging. However these are just rumors for now, so take it with a grain of salt.