A video sign displays the logo for Roku, after the company's IPO at the Nasdaq Market in New York, September 28, 2017.

Check out the companies making headlines after the bell:

Roku shares climbed more than 4% after news broke Thursday that Citadel and its billionaire founder & CEO Ken Griffin took a 5% stake in the company, according to an SEC filing. Roku shares are up more than 270% year-to-date.

Shares of Walmart dropped briefly then bounced back following an announcement that John Furner will succeed Greg Foran as President and CEO of Walmart U.S. on Nov. 1. Foran, who is taking a role as CEO at Air New Zealand Limited, will remain through Jan. 31, the mega-retailer said in a press release.

Slack's shares rose more than 1% after the company said its daily active users jumped 37% from last year. The workplace chat app's revenue grew 58% in its first quarterly earnings report since going public in June. Microsoft, which unveiled a competing messaging platform in March 2017 to all Office 365 subscribers, saw its shares rise less than 1% after the bell Thursday.

PG&E shares climbed nearly 2% after the insolvent utility announced that power had been restored to more than 100,000 customers amid a widespread power outage over wildfire concerns. The outage has affected as many as 2.7 million Californians. The utility saw its shares tank more than 25% Tuesday evening after a bankruptcy judge cleared the way for a rival Chapter 11 restructuring plan led by hedge fund Elliott Management.

Shares of SAP spiked more than 6% after the company posted strong preliminary earnings for its third quarter before dropping on the news of CEO Bill McDermott's departure. The business software company's cloud bookings increased by 38% thanks to a new cloud computing deal, the company announced in a press release. SAP reiterated its 2019 outlook for non-IFRS operating profit between 9.5% and 12.5% at constant currency exchange rates.