Ben and Loretta met for a "fight call" before the performance. Fight Call is a rehearsal held before every performance containing a stage fight. Each fight is usually run once at half speed, then once at full speed, it gives the chance to refresh choreography before the actual performance.
While trying to lie their way into a courtroom, Charles says he and Oliver are the "fathers of the bride" (implying that he and Oliver are a couple) to which Oliver replies, "Oh, that's fun!" This is a reference to the film franchise "Father of the Bride", in which Steve Martin (Charles) played the titular character and Martin Short (Oliver) was the wedding planner.
When Oliver asks if Charles has any dips in his fridge Charles says "there should be some Norwegian red herring." A "red herring" is a mystery term that means a clue or piece of information that is, or is intended to be, misleading or distracting.
Despite the title which is in reference to Mabel turning 30, this is actually the 29th episode of the show overall.