The car on the left is used in the film series Ghostbusters, in which a group of men (and women) serve as a private contract company that captures ghosts and deals with paranormal activity. The car on the right is the "Mystery Machine" from the cartoon series Scooby-Doo, which involves a group of teenagers who go around solving mysteries.

The implication of the two cars together means that things must be really bad if the Ghostbusters and the Mystery Machine need to be called in together.

Hope this helps!