This is a video of two of the FlyCroTug drones developed by researchers at Stanford University and the Ecole Polytechnique Federale de Lausanne in Switzerland that are capable of working together to manipulate heavy objects. In this example, one uses a hooked wedge inserted below a door to pull it open after the other has depressed its handle (both contain microspines on their undercarriages to anchor themselves to the carpet while pulling). Even with the world political environment aside, these are truly terrifying times we're living in. Remember to tell your kids you love them but the robots are coming and its everybody for themselves.
Keep going for the whole video. On the upside, at least they're not particularly quick door openers.
Thanks again to K Diddie, who agrees this is why it's important to switch to round doorknobs.