Conor McGregor had no trouble making the weight for tonight/tomorrow morning's fight with Chad Mendes at the official UFC weigh in last night. However, he did get into a backstage altercation before the weigh-in with his opponent's teammate Urijah Faber.
Faber was walking by McGregor and asked if he was going to be alright, given how slight McGregor looked after the weight loss. McGregor cleared wasn't pleased about it, and spoke to Fox about the incident later. McGregor attempted to play the altercation down, but it appears that it irked him somewhat.
Faber then kept firing shots by posting the incident on his instagram with the audio, complete with comparing McGregor to a crack-dealer and dismissing his wrestling abilities.
You can hear the audio in this instagram post from Faber here: