Raising the lovability quotient of a TV show that boasts the likes of furry adorable Grover, endearingly exasperating Ernie and the perpetually worried Telly Monster isn't easy. But in inventing the newest member of the "Sesame Street" family, the creators of the long-running children's classic have recognized that few things inspire appreciative smiles so readily as (awwww!) the sight of a chubby-cheeked baby.

So on today's 5 p.m. episode on Channel 26, Big Bird will learn that Gordon (Roscoe Orman) and Susan (Loretta Long) plan to adopt an 11-month-old boy. And tomorrow afternoon, the entire collection of characters will gather outside Gordon and Susan's apartment to welcome little Miles (played by Orman's real-life son).

The episodes are good examples of "Sesame Street's" unique talent for entertaining and educating toddlers and grown-ups alike. Gordon reaches out to the show's tiniest fans when he patiently explains the concept of adoption to Big Bird. "There are children who need someone to take care of them and to love them. And Miles is one of those children. And Susan and I would like to have a baby to take care of and to love. So we're adopting Miles, which means that he is going to be our son. And we'll be his parents. Forever."

Adult viewers, meanwhile, ought to be tickled by Gordon's increasing irritation with the "simple" instructions for assembling Miles' crib.

The Christmas Day program addresses problems posed by the addition of a new family member. While Big Bird straps on his party hat in anticipation of Miles' homecoming, Telly frets that love, like birdseed, is something Gordon and Susan could run out of. Gordon says, reassuringly, "You can't run out of love 'cause when you need more you just make more."

Yet part of the secret of "Sesame Street" is that it refuses to paint its make-believe world as a perfect and therefore uninspiring place. Gordon admits to Big Bird that, while the arrival of a baby may not lessen his love for Bird, it will mean that Gordon won't have as much time to spend with him.

In addition, the show acknowledges that those cuddly bundles of joy can often become inexhaustible crying machines. And although the sound of a baby sobbing may be music to the ears of Oscar the Grouch, it can be nerve-racking and bewildering for parents, brothers, sisters and neighbors. The best explanation for baby bawling comes from a Muppet named Rocky. After his room is cleared of adults, Rocky sits up in his crib, grabs a mike and belts out a tune: "I cry for a cookie, I cry for some juice, I cry just 'cause I wanna cut loose."

Clearly, the "Sesame Street" gang can expect a fair share of both problems and joys from Miles as he grows up with them. And Miles, whose shiny bald head matches that of his father, will enjoy a special childhood amid Jim Henson's creations. Already, at the ripe old age of 11 months, he appears to be up to the task. As Susan and Gordon sing "We Are a Family," Miles jumps up and down gurgling and beating his fists on the edge of his crib.

Telly Monster sums it up nicely when he observes, "Isn't it nice that they found each other?"