Upon hearing Miss Granger's suggestion, Potter adamantly refused. He turned to Ronald Weasley, who immediately was uncomfortable and threw his support to Miss Granger. After many attempts at persuasion and much consideration, Potter finally agreed to a 'small' meeting.

Little did he know that this meeting would be anything but small. Rumors flew fast, and upon walking into the Hog's Head, Potter was confronted with almost 30 students. Every house but Slytherin was well-represented. During the meeting, Potter realized that some-including Zacharias Smith, an aggressive Hufflepuff- were there to hear him tell the story of Lord Voldemort's rising at the Triwizard Tournament. After a confrontation between him and Smith, Smith stayed loyal to the group. 

By the end of the meeting, Potter had gained everyone's respect. They all signed a piece of paper, that, unbeknownst to them, had been bewitched by Hermione Granger. (Anyone who betrayed them would immediately be covered in acne that spelled out "Sneak.") 

This was the beginning of Dumbledore's Army. But no one realized that there were three people listening in to their first-ever meeting: Willy Widdershins- Muggle-baiter, Mundungus Fletcher-thief, part of the Order of the Phoenix and assigned to protect Potter, and Aberforth Dumbledore- brother of Albus, barman of the Hog's Head. 

Mundungus Fletcher would inform the Order of Potter's plans, who would unsuccessfully attempt to stop them but would ally with them in later years.

Widdershins would use this information by telling Umbridge about it. This would prevent Umbridge from arresting him for his chronic Muggle-baiting.