Ryan Wilson, 25, who plays for Glasgow Warriors, pulled Gavin Quinn from a seat in a takeaway then punched Glasgow Hawk Ally Maclay, who was dressed as Tweedledee.
Other people in fancy dress – including a man dressed as a red crayon and another as a cartoon Minion – were nearby as the incident unfolded.
Mr Maclay, 30, said “leave it Batman” after learning Wilson had grabbed his friend by his jumper and pulled him from a seat in the Barbeque Kings kebab shop on to the floor.
The former Hawks captain was hit and ended up on the floor with Wilson and Mr Quinn and several others around them.
Ryan Grant, 29, a Glasgow Warrior and British Lion, was accused with Wilson and fellow Warrior Rory Hughes, 21, of kicking and stamping on Mr Maclay to his severe injury on 27 October 2013 at the Glasgow West End restaurant.
After falling to the ground, the PE teacher was left dazed, with a fractured eye socket and bloodied face.
Following a trial at Glasgow Sheriff Court, the jury yesterday found Wilson guilty of punching Mr Maclay, but not of kicking and stamping on him, and found the charge against the other two accused not proven.
After the judgment, Mark Dodson, chief executive of Scottish Rugby, said: “This has been a wholly regrettable episode. Regardless of the verdict, there is absolutely no place in the game, on or off the pitch, for the sort of behaviour that has led to criminal proceedings being taken.”
Mr Dodson said Wilson has now been suspended, adding: “Scottish Rugby will be considering at board level what further action is appropriate and will make an announcement in due course.”
Fining Wilson £250 for assaulting Mr Quinn and £500 for the assault on Mr Maclay, Sheriff Martin Jones QC told the rugby player that both assaults “appeared to be unprovoked”, were within a short time of one another and came after drinking alcohol.
He added: “There’s nothing unusual about that situation.”
During the trial, Wilson admitted assaulting Mr Quinn, by pulling him on to the floor.
The court heard Wilson wanted to sit in the booth beside Mr Quinn so he could speak to his rugby colleague, Richie Vernon – who was dressed as a shark – but he was told to go away.
Wilson put his foot on the table in a bid to climb over into the seat, but Mr Quinn pushed it away.
He then grabbed hold of Mr Quinn and pulled him from the seat on to the floor, and there was a struggle between the men which “fizzled off”.
Mr Maclay then came in to the takeaway and was told by his friend what had happened.
When Mr Quinn spoke again to Wilson, Mr Maclay said “Leave it Batman” before he was punched by Wilson and fell to the ground.
He grabbed Mr Quinn as he stumbled back and Wilson landed on the floor with them.
Mr Maclay told the jury he was repeatedly struck and went into the foetal position in an attempt to protect his face from “numerous blows”.
He added: “There was one blow in particular that caught me right in the eye – not sure whether it was a kick or a punch or what it was.”
The victim said that was when he knew “that wasn’t quite right”.
Witnesses spoke of the fracas ending quite quickly although nobody saw any direct contact with Mr Maclay.
Euan Fraser, a Hawks fan, said he pulled Grant away from the crowd. Mr Fraser alleged Hughes later told him “Shut the f*** up or I will stab you” when he branded Hughes and Grant “a disgrace”, believing Grant was involved.
A statement from Glasgow Hawks said: “We note the two not proven and one guilty verdict. The club sees this as a conclusion to the matter and wish to draw a line under the matter.”
SCOTSMAN TABLET AND MOBILE APPS