Studio Shaft, established in 1975, is an animation studio best known for adding an almost constant stream of references and shout-outs to other series in the backgrounds of their shows. This usually manifests itself as writing on blackboards and posters which change with every cut. Also known for having a somewhat minimalist yet oddly stylish bent to their own productions. One of the more divisive anime studios. People either love the style or hate it. Middle ground is rare. Oh, and keep one thing in mind: whether the adapted work was originally a Widget Series or not, the Shaft anime will most likely be one. They were also one of the animation studios behind Jayce and the Wheeled Warriors.Akiyuki Shinbo has been their primary director since 2004, and is responsible for much of their present image.Note that some fans refer to this just as "Shaft". Do not confuse this with a badass mother— (SHUT YO' MOUTH!), or a minor character of the same name in two Castlevania games.
Enhanced on DVD: Their by-now infamous scrambling to meet deadlines during a show's original airing season generally means improved animation for the eventual DVD release. They've become so notorious for it that this practice of revising art and animation has come to be known as "Shafting", as in "Bakemonogatari was Shafted".
Retraux: They'll often add old-timey film effects or use old-timey orthography.
Schedule Slip: They're becoming increasingly infamous for this, due to a company policy of not rejecting work. Though they're generally relied upon to fix any error on their TV release come the DVD/BD release.
Justified in the case of Puella Magi Madoka Magica. Due to the 2011 Tohoku earthquake and tsunami, the final two episodes airing was delayed for over a month. Gen Urobuchi, who wrote for the series, explained that the slip came as a bit of a relief because they'd been having trouble animating them. When they finally did air on April 21st, fans could see why. Shaft loves its surreal art, after all.
Art Shift: Frequently for asides or flashbacks, the art style will be drastically different from the show's usual style. Just watch almost any five minute segment of a Bakemonogatari episode and you'll probably get an example.
Mundane Made Awesome: Shaft will often, and for no reason, up the framerate and animation quality immensely, and can focus on incredibly mundane things.
They also seem to have a thing for huge, mostly empty rooms that are, in fact, totally impractical but look artistic.
Surreal Theme Tune: All of them. Madoka Magica's makes complete sense, you just don't get context until the end.
Widget Series: Everything that they are a part of turns into this.