A traditional Jewish holiday dish. The recipe Pynchon describes may likely have come from Cooking Jewish by Judy Bart Kancigor (Workman Publishing, 2007):
If you attended Bar Mitzvahs in the 1950, you probably saw some permutation of this recipe on the buffet table. Tongue has fallen out of favor in the intervening decades, except on sandwiches in kosher delis, and even then it's ordered only by people old enough to remember that era. [...] Tongue has a soft, creamy texture and rich taste that is difficult to compare to anything else.
1 pickled beef tongue (about 4 pounds)
1 can (20 ounces) pineapple chunks, drained
1 cup canned pitted black cherries, drained and chopped
1/4 cup golden raisins
1 jar (10 ounces) orange marmalade
2 cups orange juice
1/2 cup (packed) light or dark brown sugar
1/4 cup distilled white vinegar
Juice of 1 lemon (about 3 tablespoons)
1/2 teaspoon dry mustard
10 gingersnaps, crushed
1/4 teaspoon kosher (coarse) salt, or to taste
blue lines on a stick
This refers to a pregnancy-test device a "stick" that a woman uses to see if she is pregnant. The device displays one blue line to indicate the test has worked. A second blue line, forming a + indicates pregnancy.  So, yup, a Pregnant Pause...
A traditional Ashkenazi Jewish dish prepared from calves' feet, similar to an aspic. In Eastern Europe, Jews served p'tcha with chopped eggs on Sabbath. In the early 20th century, Jewish immigrants in the United States continued to prepare the dish, and it was often served as an appetizer at Jewish weddings. But vegan?
In In Search of Lost Time (aka Remembrance of Things Past), Marcel Proust uses madeleines to contrast involuntary memory with voluntary memory. The latter designates memories retrieved by "intelligence," that is, memories produced by putting conscious effort into remembering events, people, and places. Proust's narrator laments that such memories are inevitably partial, and do not bear the "essence" of the past. The most famous instance of involuntary memory by Proust is known as the "episode of the madeleine." Here, the Tongue triggers Ernie's involuntary memory.
As Deborah Kerr, or Marni Nixon, might say, or actually sing
Marni Nixon (b. 1930) is an American soprano and playback singer for featured actresses in movie musicals. She is most famous for dubbing the singing voices of the leading actresses in films, including The King and I, West Side Story and My Fair Lady.
In 1956, she worked closely with Deborah Kerr to supply the star's singing voice for the film version of Rodgers & Hammerstein's The King and I, and the next year she again worked with Kerr to dub her voice in An Affair to Remember.