Goo #8739B (also known simply as Goo) is a planetoid composed almost entirely of a sticky gum-like substance. It's used as a Garbage Disposal of sorts, and has apparent connections to the Junkions. You can move through it easily enough... but getting out of it is another matter altogether.
The Transformers cartoon
The Autobots Rodimus Prime, Ultra Magnus, Springer, the Aerialbots and Arcee, as well as Spike Witwicky and Judge Deliberata crashed on Goo, after fleeing the destruction of Quintessa. Everyone promptly got stuck on its surface, and Springer was caught and dismantled by an alien garbage truck. Searching for the means to "shut off the goo" -- to deactivate the energy fields that kept it warm and sticky -- the Autobots were attacked by a large group of Decepticons, led there by other Quintessons.
When the Decepticons were distracted by the arrival of Galvatron, the Autobots found a control facility where they made contact with Wreck-Gar, who quickly came to their rescue. The Junkion leader used a specialized ship to melt the goo out from under them, and vacuum the Autobots inside (and spitting Judge Deliberata back out). Stymied by the escape of his quarry, Galvatron destroyed the entire planetoid in a fit of rage. 'Cause he can do that apparently.
Goo—or a twin—was later the location of a Earth Defense Command outpost, destroyed by unknown means. Wreck-Gar, Kup, Blurr, Grimlock, Wheelie and Sky Lynx went to investigate, making sure to shut off the force fields in advance this time. After finding a whole bunch of similarly broken things on the planet, Kup told his companions that this was the work of death crystals, and seconds later the entire group was attacked by Blast Off and Runamuck, the latter firing the aforementioned crystals at them. The Autobots immediately retreated from the planet. .
Whether this is the same Goo or another planetoid like it is unknown, though the number designation of the original planetoid would imply that there are thousands of the little garbage magnets.