I have never heard of Bagpuss before seeing this stamp, but hey its a puss :D It is a UK children's television series, and only 13 episodes were made back in 1974 but it remained a classic. The title character was "a saggy, old cloth cat, baggy, and a bit loose at the seams".
Come to think of it, its interesting how cats are being portrayed in the media - its hard to think of a cat character that that is overall positive..! This one might be closest to it. Thanks Eileen :))