So this is the baby stage of the 2010 June unicorn set, some of the first unicorns ever released on the site.
Way back in 2012, when I joined, these guys were uncommon with the exception of the alicorn, which was rare. Way back in 2012, I got an Advent List Snowflake Lion on Dec. 18th and, unaware of its value and afraid to ask because I was shy, traded it away for 3 of these uncommon unicorns. I willingly sent the trade, as I needed the unicorns to pay for something, and I figured "this lion is old and VR so that should cover the year difference", so it wasn't necessarily a ninja trade.
This year I celebrated my 10 year CS anniversary, and the unicorns, now all rare, have come back to haunt me.