The role of the 'tweener'
In big animation studios, the filmmaker often draws only the key frames of an animated sequence. A team of 'in-betweeners' will then fill in the missing frames—the drawings in between the key stages of a given movement—so that the motion appears fluid in the completed sequence. It is vital that the in-betweeners ('tweeners' for short) be able to submerge their own drawing style and mimic the author's to perfection. Though perhaps an underappreciated job, the experience is extremely useful for the most talented tweeners, who go on to become filmmakers themselves.
was in the habit of working alone, a stylistic stance championed by Norman McLaren of the National Film Board of Canada and by Back's producer Hubert Tison, both of whom—unlike the big animation studios—placed supreme importance on the work of the individual artist. Nonetheless, faced with the enormity of the task and ever-pressing time constraints, even confirmed soloists like Back occasionally need assistance. For Back, this was always a delicate issue. Preparing work for someone else, clarifying expectations, and checking and retouching their drawings to ensure perfect homogeneity was a real chore. Back would readily throw away many of his own drawings in order to do better ones but found it much harder to do the same with someone else's work.
Frédéric Back speaks of his need for solitude when he is working.