I've had so many friends over the years who would act WAY different if a girl was around. It's like every guy meticulously crafts a custom mask to wear when a woman is around based on what he thinks women like, or at least what he thinks that particular woman would like. With some friends I had it was like a Jekyll and Hyde situation depending on if a woman was around or not. Guys who would make super edgy jokes when it was just the boys but when a woman was around they turned into ultra woke tumblr users.
And of course I've seen tons of backstabbing all in a desperate attempt to win favor with a woman. Guys who'd fuck their friends girlfriends, guys who'd at least try to fuck them, guys who would to everything in their power to sabotage other guys in the group, guys who would lie to the girl and slander their male competition. In some cases the lies they'd spread about their own friends would be pretty heinous, with some false accusations including saying another guy had HIV and gave it to multiple girls knowing he had it but lied about it, and another being that another guy was a pedo. No truth to either of these and one of the guys even bragged about lying and having the girl believe it years later.
This is why I told myself if I ever managed to get a gf I wouldn't introduce her to any of my friends, except maybe a couple of them. If they mogged me or if they played that game where they acted dramatically different when a girl was around, I would have made sure she never met them....and that ruled out like 98 percent of all the friends I ever had.