My wife is working with some early 20th-century postcards at work, and she sent me a few scans while she was at it. I've worked with postcards from this era before and they are strange. A lot of the "humor" expressed by these cards is based on race and gender puns from a century ago, and so seems objectionable to modern taste, and other stuff is just plain weird. I usually hate the phrase "the past is a foreign country" but sometimes it does seem that they at least spoke a different language.
According to an unattributed and undated explanation on this site: "Lobster is a slang expression of contempt for a gullible, awkward, bungling, or undesirable person." I guess that makes sense.