I just watched Bill and Ted's Excellent Adventure this evening for the first time in many years. As they head through the Circuits of History, we see these green things on the circuits:
At first, they look just like sparks (similar to the blue lightning/sparks also seen). However, they appear to crawl around the circuits. At one point in the movie (just after they visit the future), Bill and Ted notice the green things: Ted says, "What is that?" and Bill says, "I don't know." We then see that they are headed for one of these green things, which looks quite monster-like, and almost reaches out to grab the phone booth:
I don't think the green monster is seen again after this, nor is it referenced in the dialog. What is this green monster in the Circuits of History?