When we were at MK, we met Gaston outside of the tavern (with a HUGE line- he's in high demand!). We found that if we quoted the song from the movie (ex. - "I see you have biceps to spare...", etc) he immediately started making other comments in regards to the lines from the song. Probably common with him, but it was hysterical!
Also, with cast members in general, just being friendly and saying "please & thank you" goes a long way! We were in MK and saw the Mayor walking down the street, and wanted to take a picture with him. We were very friendly, and mentioned that we'd love to get a great photo op since it was our friends first time.. he walked into one of the store on Main street, came back with ears for all of us and gave them to us for free and took a picture with us! It was a great moment and a great way to start the first day!