Kaka was shown a red card following a bizarre video review deep into stoppage time of Orlando City's loss to the New York Red Bulls.
Time was winding down with the Red Bulls leading 3-1 when players from both sides came together with some light pushing and shoving.
As the teams were beginning to separate, Kaka jokingly put his hands around the mouth of New York's Aurelien Collin from behind.
Collin and Kaka were teammates before Orlando traded the French defender to New York last year, and they laughed off the incident immediately.
However, MLS's new video replay system was called into play, and referee Jorge Gonzalez checked to see if the play was reviewable, then consulted a video screen on the sideline.
After a consultation, it was decided that Kaka should be sent off for violent conduct, while Orlando's Cristian Higuita and New York's Sean Davis were shown yellow cards for the initial confrontation.
"Obviously the referees don't know that Ricky and Aurelien are close friends, but when they look back at it and they see each other smiling -- I don't know, the referee is doing what he's got to do. A little bit unfortunate," goalkeeper Joe Bendik told the Orlando Sentinel.
MLS's highest-paid player is now set to be suspended, though Orlando City have the right to appeal the dismissal.
The league's disciplinary committee has cracked down on a policy regarding putting hands to the face, head or neck of an opponent, issuing a multitude of retroactive fines for the infraction this season.
The video review system was only fully implemented in MLS last weekend -- when it was used to wave off two goals -- and it was called into player a few more times on Saturday night.
Maxi Urruti had a long-range strike ruled out in FC Dallas' game against the Colorado Rapids for a foul in the buildup.
The referee consulted a video replay and ruled that Colorado's Dominique Badji had been fouled on the other end of the field. That tackle that allowed Dallas to win the ball back before a counterattack that led directly to the goal.
San Jose Earthquakes defender Andres Imperiale was sent off after conceding a penalty to the Houston Dynamo, but after review, he was allowed to stay on the pitch with just a yellow card.
The review system was also used twice in the New England Revolution's game against the Vancouver Whitecaps, first to check if a foul was inside or outside of the box, and then to see if Xavier Kouassi should have received a card for a dangerous tackle. In both cases, the play on the field stood.