The Mozart/Beethoven Connection
As anyone who studies the scores knows, Beethoven regularly borrows from Mozart stylistically, and quotes him often. It's obvious that Beethoven's piano concertos are a response to Mozart's PCs. Beethoven's #1 and #5 are beautiful pieces, while #3, it's well documented, is merely variations on Mozart's #24. It was probably the 1st written, and couldn't have been published had Mozart still been alive.
However, the 1st movement of #1 could also be called "Jupiter", as it is clearly a tip of the hat to Mozart's "Jupiter" symphony. You can sing the opening over Mozart's very famous Jupiter line, and looking at the score it's easy to see.