Those clips featuring the 30 yellow dots found in episode 1 were the brainstorm of one Clark "Corky" Gessner. In 1968, Gessner, along with Jon Stone, Sam Gibbon, Jeff Moss, and Dave Connell all left the crew of Captain Kangaroo to join the fledgling Children's Television Workshop. Gessner made several films, but were considered by the workshop to be too abstract for the format of Sesame Street, so the dot clips were the only ones that they ended up using.
Gessner also got to contribute the film about signs "In, Stop, Park, etc.) to the Electric Company.
My personal favorite of the dot films was the last one shown in Ep. 1. Where the 30 dots appear on screen at lightning speed, and then one turns red. the dot on the bottom comes all the way up and blows him a raspberry ("PTPTPTPTPTPTPTPTPTPTPTPT!!!!!!!). After nearly 40 years, I finally discovered the significance of this clip:
The empty blue field is your town. In rapid succession 30 Wal-Marts pop up around you (sound familiar?!). Big fanfare at the end. Total market domination! Except one store changes into a Target. The ghost of Sam Walton shows up and gives his disapproval "PTPTPTPTPTPTPTPTPTPT!!!!"
The end.