Check out the companies making headlines after the bell:

After being halted, Weight Watchers shares cratered as much as 28 percent after hours Tuesday after posting dismal fourth-quarter earnings and weak full-year guidance. Missing on the top and bottom lines, the weight-loss and wellness company earned $330 million in revenue, missing Refinitiv estimates of $347 million. Earnings per share were 46 cents cents, below the 60 cents forecast by analysts.

Weight Watcher's President and CEO Mindy Grossman said in a release the company "had a soft start to 2019 versus last year's strong performance." For 2019, Weight Watchers expects to earn $1.4 billion in revenue, vs. the $1.66 billion analysts estimated.

Shares of Papa John's jumped as much as 5 percent after market close on Tuesday despite weak fourth-quarter earnings. The pizza company reported earnings per share of 15 cents, missing Refinitiv estimates by 2 cents. Revenue was $374 million, lower than the expected $390 million. The company's fourth-quarter North American same store sales decreased 8.1 percent and down 7.3 percent for the full year.

Papa John's estimates full-year North American same store sales will decrease between 1 and 5 percent. The company expected 2019 earnings per share between $1.00 and $1.20, vs. the forecast $1.20.

Shares of Mylan dropped more than 9 percent in extended trading Tuesday following the release of the company's weak fourth-quarter earnings. The pharmaceutical company posted earnings per share of $1.30 on revenues of $3.08 billion. Wall Street estimated earnings per share of $1.36 and revenues were in line with estimates, according to Refinitiv. The company issued weak 2019 guidance: earnings per share between $3.80 and $4.80, vs. the estimated $5.04. Full-year revenue guidance is between $11.5 and $12.5 billion, compared to the forecast $11.86 billion.

Share of Gap ticked more than 1 percent higher in extended trading following a release that the company's board of directors approved a new $1 billion stock buyback program. The clothing company is set to report fourth-quarter earnings on Thursday. The stock later gave up some of its post-market gains.

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