When Lucius Vorenus asks Titus Pullo how his children are doing Pullo mentions that Vorena the Younger does not speak much. This is a joke referring to the fact that neither actress who portayed her had any lines during the show.
Marc Antony's line "I amuse you? ... I'm a fucking clown, eh?" is a bit of a tribute to Tommy DeVito's famous line from Goodfellas (1990): "I'm funny how? I mean funny like I'm a clown? I amuse you?"