That's right: From June 3 to July 2, there'll be a post each day highlighting Teenage Mutant Ninja Turtles canon immigrants. Now, because TMNT canon is a little confusing, it can be hard to tell what counts as a canon immigrant and what doesn't. So for the purposes of this blog, a TMNT canon immigrant is anything (a) from the movies, cartoons, video games, toy lines, or tie-in comic series that later appeared in (b) TMNT volumes 1, 2, or 4 [because they're by the original creators] or TMNT volume 5 [because the original creators are involved, it's the new official continuity, and its goal is to use as much of the diverse TMNT lore as possible].
All this week I've been featuring the inhabitants of Dimension X: Krang, the Technodrome, Traag and Granitor, the Neutrinos...but it never occurred to me until now that I could feature Dimension X as well.
It was first mentioned, as you may have guessed, in the animated series episode "Hot Rodding Teenagers from Dimension X" (December 1987). It would, however, go on to become a major part of the series, with two of the three major villains originating from there.
As with the mentioned characters above, Dimension X appeared in the Teenage Mutant Ninja Turtles Adventures spinoff comic book, but its first appearance in continuity was IDW's Teenage Mutant Ninja Turtles #14 (September 2012).
Dimension X is slightly-but-not-entirely-different in the IDW continuity. It's still home to the Neutrinos and Krang, but in this version, Krang is an Utrom, so the Utroms hail from there as well. As do the Triceratons. And each of these races lives on a different planet and they're all at war with each other.