You have probably seen the video of the interrupted BBC expert interview. More and more meetings, interviews, and even regular calls now involve video. It can be a planned webinar, or a Skype call whether the other side all of a sudden, hey, let's switch on the video.
First of all the handling of the situation. If your toddler marches in there is basically no point in keeping a straight face, trying to push the distraction away like it is an annoying insect. Apologize, pick the child up, and close the door. But it is best to prevent getting into these situations beforehand...
You see how distracting backgrounds can be. The way you positioned your work desk is almost never the best position for a camera. The best background for video calls are completely blank ones (a white wall), or completely cluttered ones a full book shelf for example. As soon as there are individual items (loose books, a gadget, other objects, the mind of the audience starts to wander of.
Adjust your attire to the environment you are in. Being fully suited up in a home office at night does not look natural. No, pajamas or sweat pants does not work either, but something in between would work better.
In short, be prepared for everything. In my case, it is my canine office friend who always comes up with a surprise...