"Armin Shimerman enjoyed watching Avery Brooks and John de Lancie film as de Lancie had been playing Q for five years at the time of the episode and “Q-Less” was just the fifth Star Trek: Deep Space Nine episode after the pilot “Emissary”. Shimerman commented: “It was interesting to watch the two of them together. It was an interesting dynamic because Avery is the lead and so he has the responsibility and that recognition in himself. Yet John de Lancie came on the set with his own agenda, which is that he has played Q quite often and is very familiar with his end and thought of us sort of as the new kids. We were the regulars, he was the guest star, but he felt like he was the regular and we were the visitors”. de Lancie replied to this: “I love that Armin quote. I think that one of the things I had to be careful about is I couldn’t be so chameleon like as to be a different character just because I was on a different set. I had to carry on in the way that I know works for The Next Generation and carry it into the new show so it would be seamless in a way. There would be kind of a bigness about Q that maybe permeates the tide pool”. (The Deep Space Log Book: A First Season Companion, p. 63)"

—http://memory-alpha.wikia.com/wiki/Q-Less_(episode)