While the group is watching Law and Order, there are several close-ups on the TV where you can clearly see the living room reflected. In these reflections, the room is empty: the couch is visible but there are no people on it.
While Ross is comparing natural gas and methane, he disregards the fact that natural gas is simply an impure form of methane. Natural gas is over 95% methane. Methane, the simplest alkane (CH4), is also odorless.
Joey tells the gang that his grandma doesn't speak a word of English. Almost immediately after that announcement, Grandma speaks several words in English. "My big fat Joey star!" She knows the names of the characters on Law & Order, and is clearly a big fan of the show. Which is in English.