Can ascaris large roundworm partially come out of anus and crawl back in? how likely is this?

Could happen: Ascaris are very large and can crawl into all kinds of places. Have seen them in the ears, coming out of the nose, in gall bladders, appendices, coughed up after being partially swallowed. Where on earth would you have become infected. If you can get one of these worms they are simple to identify, or a stool specimen will contain eggs.