Mrs. Lovett in Sweeney Todd. She is cheerful and kindly, but has no problems whatsoever chopping up human bodies nor really with Sweeney's killing, and she is really only interested in improving her social standing. While not necessarily hollow, she certainly doesn't give a lot of moral considerations to her actions.
All four main characters in the Sondheim musical Follies are Stepford Smilers of one sort or another. Their masks do fall eventually, and the comparison to their younger counterparts in Flashbacks becomes painful: back then, they had a reason to smile — at least, they thought they did. (It says something that Desperate Housewives gets many of its episode titles from musical numbers in Follies.)
In Mary, Mary, Mary accuses her ex-husband Bob of having forced her into this type when they were married:
"I felt like I was on some damn panel show, twenty-four hours a day. Smiling, affable, humming little snatches of song. Laughing when I didn't know the answers. But affable, affable, affable! You don't know how I longed to get up some morning and feel free for once to be depressed, to be constipated, to be boring."
Jennifer in When Midnight Strikes is a Type A example, the perfect hostess who is smiling and keeping the party going even though she's falling apart inside. Her song 'Little Miss Perfect' makes this very clear.
Edith in The Women has one pregnancy after another, even though she hates babies and doesn't like being pregnant. She seems to do a lot more complaining than smiling, but nevertheless insists that "I'm the only happy woman you know." Perhaps she does more smiling in mixed company.
Although he tries to seem like the stable emotional pillar of the group, the songs "Halloween" and "Goodbye Love" from Rent reveal that Mark is really one of these.
"What You Own," too.
C.B. the Red Caboose in Starlight Express: "Under the smiles and under the fun, I'm Public Enemy Number One!"
Most if not all of the missionaries in The Book of Mormon, particularly Elder McKinley. They even have an elaborate tap number, "Turn It Off", about repressing emotions they consider negative, such as memories of an abusive father, sadness over not being there for a sister dying of cancer and consequent fear of developing cancer himself, and gay feelings.