Sesame Street character played by Northern Calloway.
When engineering the Sesame Street universe - the setting was a quiet New York City cul-de-sac, it was a time capsule of late 1960s New York - they were looking for characters with which to populate that universe. Old kindly white Mr. Hooper ran the little convenience store and one episode included a polite argument about the right way to make an egg cream. Next to it was a fix-it shop run by Latino Luis and his future wife Maria.
Local residents included a nice African American couple, Gordon and Susan, and a cantankerous homeless muppet who'd built an illegal squat underneath a pile of garbage.
They were looking for a cooler "older brother" type character, a good role model - and young, Afro'd and mutton chopped "David" fit the bill. He was aspiring to be a lawyer, but after Will Lee died, a real-life event that the show used to talk about death and loss, David took over Mr. Hooper's store.
Calloway had an impressive background. A graduate of New York City's performing arts high school, he'd been a repertory actor with some chops, and became a fixture on the show. What nobody realized at the time was that he was mentally ill and progressively getting worse.
In 1980, in Nashville, Tennessee he was arrested in a suburban garage, naked from the waist down and screaming that he was David from Sesame Street and "they" were out to kill him. He'd beaten the female marketing director of the Tenneessee Performing Arts center with an iron bar, before fleeing. She was injured and bruised from her head down to her ribs, with serious head injuries. He then smashed up a plate glass window, pounded a rock through a windshield, and then entered a home and started tearing up the place, even smashing light bulbs with his bare hands.
That was actually the beginning of the end. For the next seven years the show noted a steady deterioration of his health and mental state, punctuated by bizarre episodes including him outright biting the music director of a show in a fight.
By 1989 they had had enough, and realized things were never going to get better. A storyline involving a romantic interlude with Maria from the block was cancelled, leaving her character to eventually marry her real life husband, "Luis". They literally sent the character to the farm: the story was very quietly explained in 1989 that he permanently moved to the country to look after his grandmother and her farm.
In real life, Calloway was incarcerated in a mental facility, where he lived one more year before dying at 41 of cardiac arrest after getting into a violent altercation with an orderly.
The Sesame Street world has dealt with some heavy stuff. A generation of kids remember Mr. Hooper's death and the show explaining that he wasn't coming back. They covered 9/11 and discussed emergencies and bad things that could happen, in an ininmitable Sesame Street way. Around the world, Sesame Street has had its various other country variants deal with issues: there's a Muppet in a hijab talking about female empowerment in the kind of places where women are property and chattel. There's even an HIV+ muppet in Africa explaining to children what the disease is and modelling hope of a decent life while it lasts.
But mental illness? That's a subject that even they won't touch. David simply disappeared. Sent off to the farm. The most cliche and the most lazy of excuses as to why a euthanized pet doesn't come home, or we're not going to see a teenage pregnant neighbor for a while.