X, try posting one post on this thread that is not Y was a TBG series that involves the said user commanded to not post anything related to something that they mainly post about, or else they would lose.
Origin[]
This trend started when on February 8, 2017, YouFindYourselfInJail created a topic called "PPTBG, try posting one post on this thread that is not Sonic", which challenged PrincessPandaTBG to post something that is not about Sonic the Hedgehog, in which she was a big fan of and kept posting Sonic most of the time.
Many users came upon the topic and suggested that topics like PPTBG's were created especially for them. YouFindYourselfInJail accepted their suggestions and created similar topics.