We have 3 indoor cats, all males. One grey tabby (7 yr) and 2 orange brothers (3 yr). For almost 3 years now, they've been one big happy cat family. Hallmark channel cat cute. Few weeks ago, late at night, the two orange cats were at the door looking onto the deck, completely freaked out. There was a cat outside. This cat looked exactly like our indoor grey cat. It wasn't him, he was in bed with one of the kids. Fast forward to the other night. Grey outside cat came back and one of the orange boys must have saw it and then the inside grey cat came into the room and was attacked by the upset orange cat. 4 day have passed and our one orange boy is still freaking out at our inside grey cat (his best buddy). We've kept them separated and slowly reintroducing.
Anyone have perfectly happy inside cats completely upended by a random outdoor cat outside a window?