I am not sure they should be called UFO’s but on the other hand undrafted free agents are somewhat like unidentified flying objects. They don’t get any attention during the annual MLB draft but all of a sudden make an appearance when we least expect it.
Following the 2021 First-Year Player Draft, in which the Dodgers selected 19 players of whom 12 have been signed, they have signed seven UFO’s. (The deadline to sign 2021 draft picks is 2 p.m. PT on Sunday, August 1.)
Of note, the Angels have signed 21 undrafted free agents which by far the most signed by any MLB team.