The duo is busy doing promotions for FX together, so of course they've gotten close.
"Russell and Charlie have been spending an increased amount of time together as they've been named by [TV network] FX as the stars for their summer schedule so have done a lot of promotional work together.
"Russell has invited Charlie to join him at his yoga classes. But Hollywood is a small place and everyone is worried Charlie might lead Russell astray.
"Russell is a strong guy, he won't just fall off the wagon, but he's single after his split from Katy Perry and on the look-out for women - and Charlie's legendary parties are always packed full of beautiful women."
Charlie is known for his wild antics, but we really haven't been hearing about them as of lately.
Maybe he really does just want a friend?
The source adds:
"Russell's friends are panicking as Charlie keeps calling him, chasing him to meet up. Russell is too kind to say no, he thinks Charlie just needs a friend, someone who'll look out for him. Russell was once in the same situation, off the rails and lonely.
"But Charlie is a notorious bad boy and will definitely be a bad influence on him."
Stay on the right path, Russell!
There is no good reason in the world to backtrack now!!
Charlie, be good!
[Image via WENN.]