It's a strange parallel that the most awkward scene in both The Sopranos and Breaking Bad is essentially the same. A character sings happy birthday in the style of Marilyn Monroe serenading JFK.
In The Sopranos, this uncomfortable scene drives the plot forwards, with the look of disgust on Tony's face increasing as he realises just whow this person is, and there is at least some context with her claiming to have known the president in the past. In Breaking Bad, the song shows that there is a closeness between Skyler and Ted but this is very clear later as their shared secret and, later, affair are all laid out for us.