Why did Mattel stock surge 5% today?

Mattel's stock rose 5.1% on Monday to $16.05, fueled by investor optimism following a shareholder activist campaign and a letter from Ariel Investments. The activist campaign, led by Ariel Investments' Co-CEO John Rogers, urged the company's board to consider strategic options like asset sales, mergers, or a full company sale, citing the shares' undervaluation in their current public form.

Additionally, data showed Mattel trades at around 10 times forward earnings, significantly lower than the industry average of 14 times. This pressure was compounded by reports of Authentic Brands Group exploring a takeover of Mattel valued at $6 billion or more, and Southeastern Asset Management making a similar strategic-review call in May.

The board's receptiveness to outside proposals was also bolstered by CEO Ynon Kreiz's departure and the impending appointment of Roger Lynch as CEO. The broader market also contributed to the positive sentiment, with the Nasdaq Composite hitting a record high on Monday.