I just started watching my QL Season 2 DVDs and uncovered yet a third tie-in to Magnum.
The first one was in the last episode of Season 1. At about 30 minutes into the episode, Sam (as a PI who looks a lot like Humphrey Bogart) is sitting in a taxi with his girlfriend and a nerdy, annoying other guy and says to the girl "He's gonna find out sometime that he's not going to be like Sam Spade, Philip Marlowe, or Thomas Magnum" She says "Magnum?" And the scene just goes on from there, no explanation or anything.
The second one actually was in the 13th episode of the 2nd season (which I saw on TV before I got my DVD set), when the teenage girl in the family is watching Magnum on TV.
The third one (which I guess is really the 2nd one, chronologically-speaking -- but since we're talking QL here, I guess it's OK for me to leaping around in time and space
) is in the 1st episode of the 2nd season. The main bad guy is a former French Resistance fighter named Roger. When he flicks his silver lighter to light a cigarette, a silver Croix de Lorraine is affixed to the front. Not quite as snazzy a version as Magnum's, but still clearly the Croix. They actually show it twice in the episode.
Guess I'm going to have to be on the lookout for more Magnum references as I make my way through Season 2!