Dudley had walked in on Harry doing it multiple times in the 3 years since finding out he was a freak. It didn't look hard at all, it was just a matter of when he would try it out. It had to be when his father was at work and his mum was off to the market, since he had to figure everything out. Where would he go? And what would happen if he did something wrong? Would it hurt? His parents saw Harry doing it once, which resulted in his father boarding up the fireplace. But it had since been unboarded.
The opportunity came up the following morning. His father had already left for work, and his mum had announced that she was going to a garden party, and then to the market. "Be good, Diddykins. Mummy will get you your favorite sweets." Petunia kissed her son on his forehead, and then left the house. Dudley peered out the window, watching as his mother's car pulled out of the drive and head down the street.
He hopped up, and waddled to Harry's room. He had to find the powder that Harry used, hopefully he hadn't taken it to that joke school with him. Dudley scoured the room, pocketing left behind sweets as he went. He opened up a desk drawer, and found what he was looking for. Moving as fast as his stubby legs would allow, Dudley hurried downstairs and to the fireplace. The boards were still hanging off of the entrance from this past summer when some of Harry's kind blew it apart. Man, were his parents livid.
Dudley built a small fire, and then threw the silvery powder into it. The flames burned green, which Dudley knew from observation that that was when he was supposed to step into it. Hesitantly, Dudley shuffled into the small fireplace, and mimicked Harry.
"Th-the burrow?" He questioned, curious as to where Harry always went off to. Before he disappeared into the flames, he heard the front door open.
"Duddys, I forgot my pocketbook and-" Petunia came around the corner and screamed when she saw Dudley whipping out of sight. Dudley swirled around in the nothingness, before landing and rolling out of a different fireplace. A woman's shrill shriek pierced Dudley's ears. A red haired, plump woman was standing in front of him, what appeared to be a stick in her hand pointed at him.
"Oh, you're Harry's cousin, right? I remember you from this summer, when your tongue swelled from eating those joke sweets." Molly Weasley said. Dudley stood up, cautiously, eyeing what he assumed was a want.
"Y-yes, I am.. I just wanted to know where Harry was going off to..." Dudley stuttered. The woman studied him for a moment, before lunging at him, grabbing his ear.
"It is NONE of your business where Harry goes off to. You make his summers awful, so why should you care?" Molly dragged Dudley back to the fireplace. She grabbed some of the silver powder from a flowerpot, and threw it into the flames, yelling Dudley's address as she did.
Petunia was still screaming when Molly and Dudley appeared. She was white as a ghost, and turned even paler when she saw who her Diddykins was with.
"PLEASE teach your boy some manners, it is rather rude to enter someone's place without permission. I will have the floo network disconnected from here, it seems that my husband connected it in case Harry needed a way away from you foul people." Molly huffed, pushing Dudley out of the fireplace, before shouting 'The Burrow!'
Petunia clutched Dudley to her small frame, before pushing him away and giving him a sharp smack to the hindquarters.
"How dare you use something mag- forbidden in your father and my house! You could have ended up dead. Do you understand? " Dudley nodded, then made his way back upstairs. He fell onto his bed, smiling that him and his cousin finally had something in common.