Grabbles are aliens that resemble yellow scorpions with four legs. They feed on Imaginatium, and their reproduction rate increases significantly in the presence of Imaginatium. They are not particularly violent, but attack and bite any Minifigure who approaches their food source.
Until recently, Grabbles were undocumented alien lifeforms. However, Grabbles are thought to have infested a Piratron base, leading to one specimen being brought to the Classic Space Command's MoonBase aboard a Piratron Scout Ship. When the Scout Ship was shot down, a Grabble aboard the spacecraft was able to find Classic Space Command's Imaginatium storage and reproduced in great numbers.
Grabbles now infest the MoonBase, eating the precious Imaginatium fuel rods and continuing to reproduce. To help deal with the infestation, Commander Han Nibble sends players to collect five fuel rods before smashing ten of the Grabbles overrunning the base. Grabbles are fairly easy to defeat, with only 3 Life and slow, weak attacks.
- The Grabbles' animations were designed by LEGO Universe animator Toby Cochran. In addition to the animations seen in-game, a number of unused animations are featured in an animation reel by Cochran, including a sleeping animation and a singing animation.
- Grabbles are likely inspired by the Facehuggers from the Alien franchise, as evidenced by the LEGO Universe game files, which label the Grabble as "ene_facehugger".
- Grabbles are the only enemies in the LEGO Universe that are completely unassociated with the Maelstrom.