Q is a member of Wammy's House exclusively in the Death Note film series continuity and in the novel L: Change the WorLd. Q is never seen in person, and they do not directly interact with the events of either the film or the novel.
In the novel L: Change the WorLd, Q had designed the hacking defense security systems used in Professor Kimihiko Nikaido's research lab. Q's security system was given to Nikaido by Watari. The security system is hacked by Blue Ship when they break in to get the antidote from Nikaido.