One of my favorite episodes in "Seseme Street" was were some adults actually believed Snuffy was real before they actually met him.
In this episode, as many times before, Snuffy and Big Bird were going to set up a meeting with everyone, but as expected Snuffy was a no show.
At the end of the day, the adults commented on Snuffy being imaginary. Then Big Bird boldly like never before says something like: "No he's not. He's real! If there was just one thing in my six years of life I wanted you to belive is that he is real."
Then Maria says, "I believe you, Big Bird."
Susan was still sceptical and scoffed, but Maria still believed.
In their own way, SS taught about trust and faith. Maria had noting to go on but Big Bird's word, but apparently he was so bold about it, she believed.