Tweet is a character made by Light Runner.
The original program can no longer be viewed on Khan Academy. It is pictured above. It was not animated. If someone wants the code to Tweet, they can try leaving a message on his wall here, or the wall of the founder of KAOS, she doesn't have Tweet, but she does have the code for an un-released Spin-off, Tweeta, meant to be a female version, recently seen giving Tweet a birthday balloon on his wall on KAOS.
Notable Spin-offs Edit
The spin-off that garnered the most attentions was the program that asked, "what if Tweet fell over?" and featured tweet upside down, kicking, flapping it's beak with it's eye rolling in a circle.