Accidentally found this video today. At first I thought it was from an episode but it must be for Sesame Street to get kids to brush their teeth?
No laugh track or anything, a little strange? I think it was for Sesame Street?
I'm guessing it was done around Season 5 since Henry is wearing the black T-Shirt.

Fonzie was on Sesame Street? Apparently yes!
http://thumbnails112.imagebam.com/37245/f07bac372440380.jpg (http://www.imagebam.com/image/f07bac372440380)
https://www.youtube.com/watch?v=weB3srg6o4c
I'm guessing around 1978 or 1979 because of the black T-Shirt

Another clip of him Explaining the Letter A
http://thumbnails111.imagebam.com/37244/2ac660372439787.jpg (http://www.imagebam.com/image/2ac660372439787)
https://www.youtube.com/watch?v=ZWwMre0PuTQ

http://thumbnails112.imagebam.com/37245/32fd6b372441543.jpg (http://www.imagebam.com/image/32fd6b372441543)
https://www.youtube.com/watch?v=JY3Lh2sdVI8
https://www.youtube.com/watch?v=wcR5X3Ae19Y
Explaining OFF and ON

http://2.bp.blogspot.com/-nrDzA1YPHT4/UFZ5V1kzHZI/AAAAAAAAALY/9LqOgn5WWtg/s1600/IMG_0348.JPG

I remember seeing the "A" skit back in the day.

I remember seeing the "Fonzie brushes his teeth" sketch back in the day on Sesame Street.

I also saw the brushing teeth sketch when it aired. Classic!!!!!!!!!!