‘CLIFFORD the Big Red Dog,” beloved by kids for more than 40 years, has gotten so big, he’s now small.

The producers of the hit PBS show have created a new animated series about the dog’s early years called “Clifford’s Puppy Days.”

“It’s the back-story of Clifford,” Deborah Forte, president of Scholastic Entertainment and executive producer of both shows, told The Post.

The sweet big-hearted red dog, who is the size of a house, has always helped kids to understand what it means to be different.

He was the runt of the litter and lives with his friend Emily Elizabeth, who – as the story goes – loved him so much he grew into a giant.

“Puppy Days,” debuted yesterday and will air every Wednesday on PBS, while episodes of “The Big Red Dog” will continue to air four days a week on Ch. 13/WNYW.

The original “Clifford” series began airing on PBS in 2000 and quickly turned into the highest-rated kids show on the network.

So when PBS asked them for more episodes, Forte says they decided to take Clifford in a new direction and start a series based on two of the most talked-about episodes of “Clifford” that followed his adventures as a puppy.

“We got tons of mail when we did those episodes . . . the kids loved them,” said Forte. “And they wanted to know if we were going to do more.”

It turned out to be a perfect opportunity.

“So instead of telling stories about what it’s like to be very large and trying to learn how to fit in, we’re telling stories from the point of view of being very small,” she said.