Absentee ballot mailed in by someone else?
Someone showing up at a polling place and falsely claiming to be them?
Poll workers pulling the levers on their behalf?
If your question was serious, there are numerous ways to convert fake registrations into real but fraudulent votes.
It’s called ‘helping people vote who are too busy to come to the polls’... At least that’s how it was referred to in Chicago in the 60’s...