Sometimes allies will have abrasive personalities. All too often heroes will encounter allies who are nothing but helpful (barring the cases where they are traitors undercover) and pleasant. Try introducing someone who is a genuine ally and can truly be trusted, but who just doesn't get along with the heroes and rubs them the wrong way.
General Rieekan: Hey, droid! Where's my waldorf salad?! What's a guy gotta do round here to get some lunch?
General Rieekan: You better have good news for me, Solo.
Han: No sign of life out there, General.
General Rieekan: Commander Starkiller reported in yet?
Han: Nope! Last I heard he was checking out a meteorite that hit near him.
General Rieekan: How are we supposed to spot approaching ships with all the freakin' meteor activity around here? Someone get onto it!
Han: I'll get R2-D2 onto it.
General Rieekan: No offence, but how's a stupid droid supposed to help?
Han: He's good with vectors and... space stuff.
R2-D2: Give me a planet's magnetic field and a big enough generator, and I can drill a meteor from ten million kilometres right through some meatbag's cranium. For example.