Pink slime
An organic-looking pink slime or goo, which could house alien consciousnesses, was used in 2020 as "sticking plaster" by an entity from Ecto-Space to try and fill the gaps between its universe and P.R.O.B.E.'s. The slime smelled of burnt sugar and glowed slightly. It was capable of enmeshing and capturing humans who were at the wrong place and wrong time and witnessed the process, knocking them out and keeping them tied up.
Although the entity who had brought forth the goo was well-intentioned, (HOMEVID: Goo! [+]Loading...["Goo! (home video)"]) a Living Fiction entity also entered the universe through the goo, and, when it splashed an old film reel, merged with said reel. While the reel was infused with the slime, it became indestructible, and the Living Fiction entity could project itself onto the material world from out of the film reel, adopting the form of the film's main antagonist. (HOMEVID: Living Fiction [+]Loading...["Living Fiction (home video)"])
An image of the slime was seen amidst other P.R.O.B.E. paraphernalia in a video message left to Sir Andrew Williams on the Preternatural Research Bureau Online Database. (HOMEVID: A Message From Sir Andrew [+]Loading...["A Message From Sir Andrew (home video)"])