if you go fast enough through a nether portal (you can achieve this by flying on an elytra and spamming firework rockets or a riptide trident in the rain)  you will make a glitched portal that is  invisible but braking or placing blocks will make parts of it show up going through again if you have made it show will take you far away 

MAKING A NETHER PORTAL IN THE END 

this will work but you go to the over world 

and you do not have a return portal  you can smash but that is it 

you get bored and leave and you go back in you are in the over world but no blocks are smashed