Lassie's mysterious shadow is visible on shots of the globe, coincidence? I don't think so.
It's a subtle signal 100 years into the future, for Voyager to come home.
In "One of Our Planets is Missing", views of Earth were shown on the screen as Spock mind-melded with the planet-destroying cloud. Among them, an image from filmations Lassie's Rescue Rangers... complete with Lassie! Boy, Spock has some odd memories...
Maybe Lassie was trying to tell Spock that
Timmy fell down a wormhole?
Been a VERY long time since I saw animated Trek.