Yet instead of being welcomed, Galloway's appearance prompted a mass walkout at the event, and the party leaders' partnership is now the subject of intense scrutiny - and mockery.
Nigel Farage and George Galloway stand with other Grassroots Out leaders on Friday
Rather than persuading voters of a cross-spectrum rationale for Brexit, many said that Farage and Galloway's pact was helping them choose to remain within the EU.
However, it wasn't only the pair's ability to persuade voters that was the subject of discussion online.
Previous statements made by Galloway quickly came to light, including his criticism of Farage's reference to HIV/Aids treatment costs during a General Election debate.
Galloway also appeared to liken his pact with Farage to that of Soviet leader Stalin and Winston Churchill's during World War II.
And there's been plenty of jibes after the tie-up was revealed.
Despite the walkout at Friday's Grassroots Out rally, the more than 1,500 people who stayed in the hall for Mr Galloway’s speech gave him a rousing reception as he called for the UK to leave the EU.
He talked up reconnecting with the Commonwealth, access to more trade markets and the reassertion of sovereignty as the key reasons for Brexit.
Labour MP Kate Hoey, former Shadow Home Secretary David Davis, Tory MPs Peter Bone and Tom Pursglove and economist Ruth Lea were among those to speak at the rally.