It's pretty simple. After this tweet by Dan Barker got thousands of retweets...
...this became a thing.
And so on.
It's beginning to spread beyond Twitter.
Barker, the guy who started the meme, told BuzzFeed News:
Just as Craig David eventually found peace with his Bo Selecta taunters, I hope Russell Brand can eventually forgive me, along with Damon Albarn, Phil Daniels, and @paperclipracket, who pointed out he'd made the observation before I did (his was funnier too).
Explanation for confused American readers: Basically, people in Britain have realised that Russell Brand sounds exactly like Phil Daniels in Blur's 1994 hit "Parklife".
Now everyone's making mashups because that's the internet.