<!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--> <!--You can feel free to delete the sections that do not apply.--> ### Bug report **Bug summary** see title **Code for reproduction** <!--A minimum code snippet required to reproduce the bug, also minimizing the number of dependencies required--> ```python plot([[0, 1, 2], [3, 4, 5]], [[0, 1], [2, 3]]) ``` **Actual outcome**  This plots column 0 of x vs column 0 of y; column 1 of x vs column 1 of y; and column 2 of x vs column 1 of y. **Expected outcome** Error out with non-matching shapes (the 1 -> broadcast should remain possible). https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/axes/_base.py#L393 should probably be replaced by a broadcast. **Matplotlib version** <!--Please specify your platform and versions of the relevant libraries you are using:--> * Operating system: * Matplotlib version: master, probably around forever. * Matplotlib backend (`print(matplotlib.get_backend())`): * Python version: * Jupyter version (if applicable): * Other libraries: <!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--> <!--If you installed from conda, please specify which channel you used if not the default-->