Martin O'Neill and Chris Sutton made a memorable return to the place where they launched their Celtic careers as the visitors produced some festive fireworks to stun sad Dundee United.
The visitors looked in the festive mood from the off with Sutton, Larsson, Didier Agathe and Bobby Petta all causing all kinds of problems.
Larsson was handed the best early chance in the 17th minute when David Partridge let Douglas' clearance bounce and Larsson hit a right-foot shot from just inside the box that Alan Combe did well to save.
But the goal Celtic had been threatening finally arrived in the 23rd minute and it came from the penalty spot after Aljofree was judged to have brought Larsson down in the box.
The Swedish international striker stepped up himself to blast the ball home.
Sutton should have opened up his account in the 32nd minute when Ramon Vega picked him out in acres of space at the far post, but he somehow headed wide.
Sutton, however, made amends just two minutes later when Petta showed a great burst of pace to leave the United defence in his wake before sliding the ball across the face of goal for Sutton to side-foot home from close range.
Celtic were refusing to show any Christmas spirit to their opponents and in the 41st minute they wrapped up the points when Sutton rose to head Lennon's free-kick past Combe and into the top corner.
The travelling green and white army that had braved the snow and freezing conditions were warmed up further in the 73rd minute when Petrov got in on the act as he side-footed home Agathe's cross-come-shot.
Dundee Utd: Combe, De Vos, Griffin (McCracken 73), Partridge, McQuillan (Davidson 68), Buchan, Miller, Easton, Aljofree, Hamilton (Winters 75), Thompson. Subs Not Used: Heaney, Gallacher. Booked: Aljofree, Partridge, Miller.
Celtic: Douglas, Mjallby, Vega, Valgaeren, Agathe, McNamara, Lennon, Petrov (Johnson 79), Petta (Smith 79), Larsson (Moravcik 79), Sutton. Subs Not Used: Gould, Boyd. Goals: Larsson 22 pen, Sutton 33, 40, Petrov 72.
Referee: H Dallas (Scotland).
