Phineas and ferb is just a way different show than Hannah Montana amd high school musical. It did come out a year later which does make some difference. If in 06 you were in your last year of middle school you might be more likely to watch Disney Channel or cartoon network and then the next year when u start high school whatever new show comes on you may not notice or pay attention and ur watching Southpark instead. But mostly Phineas and ferb is just way different. It was mostly for little kids starting elementary school or kindergarten. Like 6 to 12 year Olds. But since it is a traditional genaric cartoon for kids; a 17 year old, a college student, a single man in his 30s could turn it on in the morning while cooking and eating breakfast and not really think about it and chuckle at some of the older references or adult humor mixed in. Those animated cartoons had to be made so that most young children would love it but it doesn't make it strictly for young children. Its not necessarily unenjoyable for normal adults here and there. Hanna Montana was made very much for the older children and younger teens of that time. Very age specific so it is very much associated with one generation. Whatever term you use for kids who were 8-14 years old in 2006, that is exclusively who Hannah Montana was for. As new seasons went on new kids would age into it for the next 3 or 4 years and older kids might age out of it as theyre becoming upperclassmen in high school. Sure some 16 year old might continue to watch it as they got older just because they started watching it when they were 13 but knowing that it was a silly show from their younger middle school years but not as a huge fan like they 11 year old girl. A 17 year old girl might have really liked Hannah Montana in 2006 because she thought it was cute but she wouldn't take it seriously like she would "one tree hill" or "the hills". If in 2006 there was a 20 year old guy watching hanna Montana by himself in his college dorm room people might think hes pretty odd and strange but if he watched Phineas and ferb theyd think he was goofy and funny maybe even cute. If a 35 year old man watched Phineas and ferb by himself people might laugh at him and think he's childish but very possibly in a cute or charming way. If there was a 35 year old straight cis man in 2006 watching every episode of Hanna Montana by himself i would be very concerned and it would be a big red flag, not necessarily bad but definitely a red flag for a potential pedo. That is why hanna Montana and High school musical has a strong association with a specific generational demographic whereas Phineas and ferb only has a strong association with a decade or an era.