When Velma Dinkle, the main character in the adult-animation series, about the origins of the future member of the Mystery Incorporated gang, encounters Fred Jones, he makes an excuse for not having remembered Velma's name. "I have a disease where I can't recognize people who aren't hot," he says. "My doctor says it's basically sickle cell for rich people."

"Is it called rudeness?" Mindy Kaling, the voice of Velma and an executive producer on the show, quips.

Then Fred, voiced by Glenn Howerton, answers earnestly, "It is! You're, like, smart."

Not many viewers were laughing.

"What might've started out as a harmless joke, turned out to show a lack of empathy, compassion for & knowledge of #sicklecelldisease," one advocate tweeted.

Another added: "To associate sickle cell to 'rudeness' is extremely harmful."

According to the CDC, sickle cell disease is a group of inherited red blood cell disorders which affect the shape of the cells that carry oxygen throughout the body. As a result, the patient faces a constant shortage of red blood cells, which can result in severe pain and other serious health complications. About 100,000 Americans, mostly Black Americans, are affected; the CDC estimates that it occurs 1 out of every 365 Black or African-American births.

The non-profit organization Sickle Cell 101, which is dedicated to education on the topic, asked followers for their thoughts. They answered that they found the Velma mention "terrible," "offensive" and "not funny at all."

Reps for HBO Max and Kaling did not immediately respond to Yahoo Entertainment's requests for comment.

But the backlash isn't the show's only challenge. On review aggregator Rotten Tomatoes, Velma has earned a paltry 42%, based on 33 reviews. Meanwhile, the show's audience score, based on more than 10,000 viewer reviews, sits at just 6%.

Still, ratings have been better. The Wrap reported Jan. 25 that the show had seen a 127 percent increase in demand in the previous week (it debuted Jan. 12), making it overall the second-most in-demand freshman show of the week.