Riding up front in the old Mercedes station wagon of his new owner (a "besotted" Bill Peisley from Queanbeyan), Cooper brushed off questions about the disappointments that had dogged his past six months at the shelter.

After being surrendered in November, the two-year-old bulldog boxer cross watched on as the shelter emptied around him during the February adoption weekend.

Instead of a home, Cooper found overnight celebrity,  sparking an outpouring of love on social media that quicked turned into lines of people waiting at the gate to meet the eligible pooch. But it would be another two long months before he could head out those gates himself.

"He's a superstar," Mr Peisley said.

"I didn't realise how famous he was. Adopting him was like going for a job interview or taking home someone's daughter. There were so many questions."

That's because Cooper was a little pickier than most pooches, in need of a firm hand to continue his training.

"He's a big sweetheart, but he doesn't know his own strength, he needs someone strong, who can hang onto that lead," the RSPCA ACT team said.

"I don't think we've ever had an animal this popular, except maybe Chris the Sheep."

Mr Peisley kept staff in suspense until late Friday afternoon, visiting three times "to nut it out" and speak to his behavioural trainers.

"We almost thought he'd changed his mind, then he came right at the end of the day," staff said.

On the front steps of the Weston shelter, they gathered for an emotional send off.

"They were almost in tears, he’s that sort of dog that really gets his hooks into you," Mr Peisley said.

But Cooper's new owner has promised to bring the boisterous dog back to visit RSPCA staff every few months. He admits he has also joined a gym "to keep up with him", and spent the weekend introducing Cooper to his new stomping ground on long walks along the Queanbeyan river.

Mr Peisley had been in the market for a dog, on and off, for a while, at the insistence of his sister who rehomes boxers in Queensland.

The week Cooper was left behind at the RSPCA, Mr Peisley saw The Canberra Times story circulating on Facebook, and before long, he was inundated with friends urging him to take Cooper home.

"I went there and he was pretty full on, jumping on me, but then during the second visit, he snuggled up against my leg and from that point on, he had me, the rest was just working out the finer details."

Since learning better manners at the RSPCA, Cooper has mellowed and become "quite well behaved".

Mr Peisley reports he is already settling in easily to life over the border, cruising around in the old wagon during the day and listening to jazz in the evenings.

"I bought him a bed but I'll admit he's been sleeping cuddled up with me."

With a slightly slobbery kiss goodbye for this reporter, Cooper climbed back into the Mercedes.

"He's a cool little guy,  he just needed the right one," Mr Peisley said.

"I did too."