Let's begin with Muriel and Eustace. When they got married, Eustace was pretty much a grump thanks to his parents and older brother. But was not as bad as he was when the show began. With Muriel, he was more loving and with Courage, he was more tolerant of him. Especially since he was still a pup at the time. As for the kind, old woman we all know and love, she was just as bubbly and sweet as she is now. But with Courage, he seemed to gain a bit of paranoia due to his parents' departure. Making him be overprotective as a result.
But then came about a year or two later and the Bagges were blessed with a baby; a girl whom they had called "Kitten". As the child grew up, she became more and more of a pleasure around the house, especially with her father who became more lovable because of her. And Courage looked on the kid as a little sister. But things slowly started to change when young Kitten began to take up a talent for music. A trait she had inherited from her mother, but instead of a sitar, Kitten practiced her skills with a guitar. Years later, the now 18 year-old Kitten was ready to leave the Nowhere Farm and venture into her own musical path. With her folks' blessing, of course…and to poor Courage's woes of losing one of his few friends.
Fortunately, Kitten had returned four years later with her new-found fame and fortune. And with those two things, she got her family out of the raggedy farm and into a luxurious house. It wasn't long until there would be a house warming party where the video above took place. Yet, the reason why Courage would be so worried would be due to being concern about how exactly Kitten got so famous; hard-work and dedication…or something far more sinister. Still, after having to get used to Kitten again, their relationship rekindled into the brother-sister duo they once were. Sadly, it would not last for long.
This was because when Kitten went off to tour, she vanished. Leaving most to think she was dead. The Bagges at first believed it was the former; she was alive but is missing. They had paid big money for her to be found but nothing came up. Soon, bills began to rise on the mansion with money the small clan couldn't even pay anymore. So, they were forced to move back to their old barn in the middle of Nowhere. With Kitten still gone without a trace.
While the years went on, Eustace began to lose hope and became bitter, thus taking it out on Courage. Muriel still has faith but would often act out in ignorant bliss as her way to move on. Though, when thinking of her long-lost child, she would be greatly depressed and stop herself from thinking about it. And as for our favorite cowardly dog, Courage would miss his surrogate sibling greatly but couldn't confide this to Muriel, for he doesn't want to cause any more pain to his beloved owner. Still, Courage moved on with Kitten's memory and with more urges to protect his home.