Thing is, it's recognisable characters.
Maxi-Minor_Furie absolutely HATES Bob the Build and Thomas the Tank engine. He will not sit through more than a minute of either program.
Yet, Drayton Manor to him is "Thomas Land". As in "I want to go to Thomas Land". He only spends five minutes each visit there, but it's a recognisable hook, it's allowing him to enter the world created on the small screen.
Likewise, we go to Butlins each year and they have "Bob the Builder Yards". It's just a small fairground with some very ropey themed Bob rides (ie, they have nothing to do with BtB other than the giant Bob stood outside). Again though, the place sticks in the kids minds. They want to go there - it's a recognisable franchise they can experience.
Peppa Pig started when Maxi-Minor_Furie was about 18 months old - it's a three year or so old franchise now. At first, we thought it was a little too cult to be big. If you're a parent, it's actually a fantastic show.
Firstly, for the right age group (under fours really), it introduces "big world" concepts and explains them and puts them into perspective in a fun way. It may be about tidying up, going to the dentist, experiencing fog, Dad doing DIY, washing the car - lots of simple, mundane things we take for granted. Things though which are new, exciting and perhaps even scary to a child. Peppa Pig deals with them all in a brilliant way - seriously.
Secondly, it has an underlying humour the parent's will understand. It's quite subtle, but it's a very clever parody of modern family life. So if you actually watch it with your kids, you will both get a lot out of it.
Does this mean it will be popular forever, and deserves a "world" of it's own? Probably not (the creators have already moved on to 'Ben and Holly's Little Kingdom'), but it is still a world kids can recognise and step into. It will be brought to life and they will love it. It's spot on for the age range Paultons go for and it will prove to be extremely popular - mark my words :)