The tag "regular-show" refers to a porn video that features content related to the animated television series, Regular Show. This show is an American animated television series created by J. G. Quintel for Cartoon Network. The series focuses on two roommates and best friends, Mordecai (a blue jay) and Rigby (a raccoon), who frequently get into various misadventures while working at a park in their fictional world.
The porn video tag is related to the context of the series, characters, or any adult parodies or fan-made content inspired by it. These videos may not actually include scenes from the show itself but rather use elements and themes from the series to create new adult scenarios, often involving the characters in explicit sexual situations.
In short, a "regular-show" tagged porn video would be focused on content related to or inspired by the animated television series, Regular Show. It is intended for an adult audience familiar with the show.