While no one actually believes that 40-year-old Mayweather, who easily outboxed McGregor in their boxing superfight last summer, will ever step into the Octagon and allow himself to get destroyed by McGregor in an MMA match, it's still fun to see these two duke it out on Twitter.
What are the chances that this fantasy UFC fight actually happens? Zero.
But at this point, combat sports fans would love to see McGregor break his long absence from the Octagon and face an actual MMA champion. Dare to dream.