Nicole MacCorkle carries giant panda cub Bei Bei at the National Zoo in December. The public will get to see him at the panda house Saturday. (Matt McClain/The Washington Post)

Five months after the doors were closed to the public at the National Zoo’s giant panda house, keepers are scheduled to unlock them at 9 a.m. Saturday to let the masses see for the first time, in person, the cub named Bei Bei.

There won’t be hoopla or baby streamers, the zoo says, but long lines are expected as people get the chance to see the 25-pound, black-and-white bear that has grown dramatically in size and strength.

“It’s going to be just a great day in the panda house,” said zoo spokeswoman Pamela Baker-Masson.

“Everyone’s been ready for this, waiting for this,” she said. “Our supporters and enthusiasts finally . . . get to come and see him in person.”

Friends of the National Zoo got special glimpses last week, but Bei Bei’s public debut — and the latest chapter in Washington’s love affair with pandas — starts this weekend.

The Smithsonian National Zoo’s four-month-old giant panda Bei Bei was still cute to watch, despite not having a whole lot of energy during her big media debut. (Ashleigh Joplin/The Washington Post)

No longer the helpless creature he was at birth, nor the sleepy armful he was a few weeks ago, Bei Bei now has attitude and heft, the zoo says.

Three keepers had to abandon an attempt to draw his blood Tuesday because he resisted so vigorously.

“He is a bear,” said Brandie Smith, the zoo’s associate director for animal-care sciences. “He’s at the point where he’s unwieldy enough” that keepers can no longer compel his cooperation: “After a few attempts, we decided to let him go on his way.”

“He’s big enough that he can decline, and we can’t make him,” she said. “He’s very active, very boisterous. He’s moved from the baby stage to the toddler stage. . . . Now, he has control over all four limbs and he likes testing them out.”

As he grows, the zoo staff is increasingly careful with him. “Only the trained keepers in the panda house who are familiar with him and can read his behaviors go in with him,” Smith said.

“There are moments when he wants to challenge them, to show them that he’s a tough male,” she said. “There are times that he’s more playful. There are times that he’s sleepy.”

Giant pandas have powerful jaws — with large, sharp teeth — and huge claws. Full grown in about six years, Bei Bei will probably weigh about 275 pounds.

Before that, a time will come when keepers will go into his area only in pairs, Smith said. Later, keepers will only go in if there is an emergency, she said. Then, it will be too dangerous to go in with him at all.

But for now, he is still nursing, and still has not been outdoors. That step will probably come in the next few weeks, when his mother, Mei Xiang, decides he is ready. She will indicate that she wants to take him outside by pushing him toward the door, Smith said.

“It’s bringing him out of his den into the wild,” she said. “That’s something that would happen [naturally], so we let her control that behavior.”

The zoo said that it has been gradually increasing the number of staff and visitors to the panda house to avoid shocking the cub with a big crowd Saturday.

Bei Bei, whose name is pronounced “bay bay” and means “precious treasure” in Mandarin, was born at the zoo Aug. 22, along with a twin that died a few days later. It was the third time that giant panda twins had been born in the United States.

The zoo’s adult male giant panda, Tian Tian, fathered both cubs after the mother was artificially inseminated in the spring with his semen and that of a panda in China.

Bei Bei has an older sister, Bao Bao, who was born at the zoo Aug. 23, 2013, and still lives there. He also has an older brother, Tai Shan, who was born in 2005 and lives in a panda conservation center in China.

The birth of Bei Bei and his twin, who was never named, posed a problem for the zoo. Panda mothers often have a hard time caring for two cubs, and usually only one survives.

The zoo tried switching the cubs — leaving one with Mei Xiang while keepers cared for the other. Then the keepers would switch the cubs back, so each got time with the mother.

But after several days, it appeared that the smaller twin was sick.

The cub, which weighed only three ounces, had contracted pneumonia after inhaling formula it was being fed by keepers, the zoo said later.

Zoo veterinarians placed the cub in an incubator, pumped in oxygen and administered antibiotics, fluids and nutrition. Nothing worked. The cub went into cardiac and respiratory arrest and died at 2 p.m. Aug. 26.

The zoo’s staff members were devastated, but they still celebrated the survival of Bei Bei.

The new cub was named at the zoo Sept. 25 by first lady Michelle Obama and the first lady of China, Peng Liyuan.