Sian Cosgrove, 24, said she had not spoken to her neighbour in Leeds despite living opposite for almost a year, but decided "what have I got to lose?"
With that in mind, Ms Cosgrove, who is a trustee at Support After Rape & Sexual Violence Leeds, wrote a sign that read "WHAT IS THE BLACK + WHITE CAT CALLED?"
The neighbour responded with a window sign of their own that read "WALTER" and a relationship was born.
"He's an inside cat that lives over the road," Ms Cosgrove told the PA news agency.
"Me and my partner had been calling him Eric because we didn't know his name, but he was always sat in the window looking majestic.
"It was annoying me that we didn't know his name but we see him every day (all day every day now we're in lock down) so I asked!
"I didn't expect to get a response but they were really good sports about it."
The messages between residences continued, with Ms Cosgrove writing another sign that read "GREAT NAME, WALTER IS A HANDSOME BOY" and the reply reading "HE SAYS THANK YOU".
And while the exchange has delighted people on Twitter, with more than 750,000 likes on the original post, Ms Cosgrove said it has helped her during the lockdown too.
"Feeling part of a community has felt huge for me while we're in lockdown," she said.
"We've lived here for nearly a year and never spoken to them, but I figured what have I got to lose. I was so chuffed when they posted something back!"
Ms Cosgrove added that she had sent a note to Walter's owners that read "WALTER IS NOW TWITTER FAMOUS... SORRY".
Walter's humans replied with their cat's brand new Instagram handle, which already has more than 5,000 followers.