In the MLP ‘n Friends episode “Tambelon”, its established that Grogar’s dark city of Tambelon exists in a different dimension; every 500 years it phases into the ponies’ dimension. Unicorns can get stuck in Tambelon before it even appears, as their winking (aka teleporting) briefly takes them through other planes.
When Tambelon physically materialized into Ponyland, Grogar captured every pony, plus magic users like the Moochick. But Megan and the ponies defeated Grogar, sending him and Tambelon back to their original dimension.
Then there’s the other G1 series, MLP Tales, which is a mundane world. The ponies drive cars and attend school, they’re all Earth ponies, and there’s no magic . . . or IS there?
MLP Tales has two mystical occurrences: the ghost of Squire appears and the magical Glow ‘n Show ponies (three pegasi and one alicorn) rescue Patch.
So what if Grogar came back 500 years after Megan & friends defeated him? And what if the new generation of ponies once again defeated him--but THIS time most ponies were unable to escape the city before it dematerialized. Perhaps only a few Earth ponies remained in Ponyland, gradually repopulating it. And as the years went by, unicorns, pegasi, flutter ponies, etc, became little more than myths.
So my theory is that another 500 years have passed and Bright Glow and her Glow ‘n Show friends have managed to escape from Tambelon before it fully materializes and are now scouting, looking for information and allies to free their trapped friends and defeat Grogar once and for all.
