Check out the companies making headlines after the bell Monday:
Pep Boys stock soared in extended-hours trading. This move came on the heels of activist investor Carl Icahn's increased bid against competing tire company Bridgestone to acquire Pep Boys. Icahn is the second-largest shareholder with more than 11 percent of the auto parts company.
Rambus shares also climbed higher in after-hours trading. The technology company announced Monday that it has renewed its patent license agreement with Toshiba.
Kohl's stock inched lower after the bell on Monday at a time when online retail is hurting brick and mortar sales. Kohl's stock is down more than 22 percent year-to-date.
Fitbit shares climbed higher in after-hours trading. The wearable fitness device maker's app (free app) in Apple's app store on Christmas Day.
Shares of Willis Group Holdings jumped in extended-hours trading. The insurance company announced Monday that it is set to replace Fossil and join the S&P 500 after the close of trading on Jan. 4, 2016. Willis Group is scheduled to merge with Towers Watson around the same time.
— The Associated Press contributed to this report.