World Youth Day pilgrim was taken away in a police van for attacking a demonstrator on Oxford Street.
The pilgrim allegedly approached the local demonstrator, Stefan Joksic, of Newtown, and jumped on him and called him a "fag", before being taken back to Taylor Square with police.
Police on the scene would not comment on the incident but demonstrator
Stefan is joined by a devil, a drag queen and a pink alien are opposing Pope Benedict XVI's stand against condoms, homosexuality and abortion.
They are part of a colourful crowd that assembled at Taylor Square in east Sydney's Darlinghurst on for a planned march towards Randwick Racecourse, where the Pope will hold mass for up to 500,000 people.
Many of the hundreds of people rallied by the NoToPope Coalition, were wearing shirts emblazoned with slogans including "Bless me father for I am homo", "Thank God I'm an atheist" and "If God hates fags then I hate God".
They were joined by a devil bearing the sign "I do not exist", the fluorescent pink alien the Raelian Movement has named Pope Alice, along with drag queen Vanessa Wagner.
The coalition won the right to "annoy" World Youth Day (WYD) pilgrims in a court battle earlier this week.
The Federal Court struck out the section of the clause in WYD regulations that made it illegal to "annoy" participants, punishable by a $5,500 fine.
However, it is still an offence to inconvenience pilgrims.
"We did it, we made it here," NoToPope Coalition spokeswoman Rachel Evans said.
"We're really happy with the turnout.
"I'm especially happy with all the gorgeous T-shirts and placards showing gay pride is alive."
A total of 6,000 condoms, red in colour to promote HIV awareness, will be offered to WYD pilgrims during the protest march.
The coalition argues the Pope's views constitute a conspiracy to murder, because opposition to condoms leads to more people becoming infected with HIV.
NSW Police Commissioner Andrew Scipione said he hoped Saturday's demonstration would remain peaceful.
