You mean like creating house rules for an established game? Yeah, my college friends and I played our own variant of Uno, called Mortal Kombat Uno. It was the same as the regular game, with four rule additions:
1) Draw Until You Can Play: If you can’t play a card, rather than drawing one card and then either playing or passing, you must continue to draw cards until you draw a card that can be played.
2) Stacking: If someone plays a Draw Two on you, and you have a Draw Two in your hand, rather than drawing 2 cards, you can play your Draw Two. Then the next person must draw 4 cards – unless they also have a Draw Two, in which case they can play it. And that continues until someone can’t play a Draw Two, and that person must draw 2 cards per Draw Two that was played up to them. The same rule applies for Draw Four Wild Cards.
3) Feeding: If someone leaves the table (to use the bathroom, get a drink, answer the phone, etc), the game is not paused. Instead. when it is their turn, they are given (“fed”) two cards and then skipped.
4) Mortal Kombat: When you have an identical copy of the card most recently played, you may play that card, regardless of whose turn it is. You must play your card before the active player is able to play their own card. Play then continues on from you. This can also work in conjunction with the Stacking rule as described above.