As Warner animation fanatics know, the WB cartoon studio shut down for a few months in 1953 when Jack Warner decided that movies were going to go 3-D and it wasn't worthwhile to produce cartoons in 3-D. When he realized that 3-D wasn't going to catch on, he re-opened the cartoon department. Some animators didn't come back, but many did. The budgets, which had been getting smaller (or at least weren't keeping up with inflation), got smaller after the shutdown, the animation got more limited, and in general, while many people including Greg Duffell have called the early '50s one of the best periods for animation at Warner Brothers, hardly anyone says the same about the late '50s. See for example Gerry Chiniquy, a good animator in the '40s, but whose jerky style became a bit self-parodic when he returned in 1954.
But there's one animator at WB whose work seems to me to be a lot better after the shutdown, and it's Art Davis. His work as an animator at Warner Brothers in the '40s and early '50s (before and after his stint as a director) was terrific, but it seems to me that it's sometimes hampered by what looks like poor in-betweening. Or at least in-betweening that doesn't really connect Davis's drawings in a logical way. This isn't so much a problem in the '40s before he was directing at the studio, but it's very noticeable to me in his scenes in Friz Freleng cartoons of the early '50s, which are very choppy because the characters don't transition well between one pose and another. His scenes almost wind up looking like a series of still drawings.
For some reason, after the shutdown, from 1955 on, Davis's scenes become much more fluid and less choppy, and his animation actually seems more loose and wild and free, which you can't say about almost any other animation in the late '50s. I don't know if he had new or better in-betweeners or if something changed in his style, but he's the only WB animator I can think of whose animation actually improved in the late '50s, though I wouldn't necessarily go so far as to say it's his best animation ever, since his work in the Tashlin unit in the '40s is awfully good (it's hard to top some of his scenes in "Two Crows From Tacos," or Sylvester at the radiator in "Birds Anonymous," though).
For comparison's sake, here's a Freleng cartoon from 1950, "Mutiny on the Bunny," not on DVD yet; I think Davis does the first scene with Bugs and Sam on the boat ("Oh, yes you are!"). Another choppy-looking Davis scene is the first shot of Sam in "Ballot Box Bunny," where the drawings are great but Sam almost freezes into each one of them.
And here's one of the first cartoons after the shutdown, "Tweety's Circus"; Davis does a lot of the animation, including the opening with Sylvester singing and the scenes of Sylvester hitting the lion, and to me at least, it looks better than his earlier animation for the studio.