The Sun says the Hoff, in panto in Manchester, joined the Etihad aces in the dressing room after the champions' easy victory.
The former Baywatch star and Britain's Got Talent judge said: "There is nothing better than to go and watch City win on your day off.
"I'm into the spirit. I know how the city is separated between City and United.
"I'm torn between the two clubs. I want to wish everyone a 'Hoffy' New Year."