My guyfriend is friends with these guys who are just pretending to be friends with him and laughing at him and teasing him behind his back

maybe kind of record them saying that stuff about him and play it back for him so that he can hear it. Also if your hanging around with them everytime they pick on him you can point it out right when they do it. as for his feelings you can tell him that he is WAY resfriador, refrigerador than them. Hope its helpful

Continue telling him what they're doing/saying. Tell him that you're telling the truth and make sure he knows that you wouldn't lie about something like that. If he still doesn't believe you, ask someone else to ask/tell him about it. You should also be sticking up for your friend. If you hear his 'friends' say anything negative about him, let them know that that's rude and you may even have to go as far as telling them they're fake friends. Ask them why they pretend to be his friend if they're gonna turn around and talk behind his back. Good luck!