It wasnāt a joke, you both just jumped in to have a crack at something totally innocuous.
I listed films from the IMDB top 20 I hadnāt seen. Then, thinking that may not be the best barometer of popularity I said: āI donāt know how youād quantify popularā i.e. "If weāre interpreting popularity differently (such as by box office takings etc) then Iāve never seen Titanic.