A rough half/less than half of the film would be sufficient. The whole "everything is new to us" exploration of the outside world should be kept to a cliche ridden minimum, and any time spent outside should be useful to the plot.
I'd use the Sesame Street film Follow That Bird as an example. There's a LOT of time spent, all useful, with Big Bird out on his own and his friends following him, cutting back to Sesame Street and the characters not involved with the chase comment on the events taking place.
Something like that, but with Doozers and Gorgs. I'd hate to separate the main Fraggle Five for too much of the movie.
I'd use the Sesame Street film Follow That Bird as an example. There's a LOT of time spent, all useful, with Big Bird out on his own and his friends following him, cutting back to Sesame Street and the characters not involved with the chase comment on the events taking place.
Something like that, but with Doozers and Gorgs. I'd hate to separate the main Fraggle Five for too much of the movie.