When in Paris

I am in Pareeee for the expo, and, as usual, using my pretty convincing French accent and Gallic shrugs to fool waiters into thinking I can actually speak the damned language. I can usually make myself understood, with many crunching gears as tenses and verb endings are treated more as Platonic ideals than actual grammatical rules, but the problem with translation is not necessarily understand what the individual words say, but a grasp of idiom as well. Take this poster as an example:
French poster
I understand that the top line translates as “Your new best friend”, so I'm assuming the French call dogs man's best friend too. I understand that in response to one dog's question “But what does it have that we haven't?”, the other answers, “Dog, Oscar, dog”, and I imagine that there is some hilarious play on words there – ‘chien’ meaning both simply dog and something else – but without knowing what that ‘something else’ is, the whole thing takes on a surreal quality which is only heightened by how dazed I already am from this whole expo thang. Bleh.