Bumbleflower, Hazel spiked high soon after its release and quickly crashed back down
Their whole deal is that they have a special elixir which, when imbibed, will let a Time Lord regenerate into whoever they want to be (in the Doctor's case into John Hurt, aka The War Doctor)
This means you can go off from nothing but an artifact or two in play for six mana, which is an explosively powerful thing to do in Standard
They've always been a great way to remove pinpoint enemy units
You can sacrifice your entire board to pump an evasion creature and Galvanic Blast them for lethal, but if they Lightning Bolt or Path to Exile in response to you trying to move modular counters, you are in hot water
There has never been blue common which so defined an entire color in a limited format, and for that Capsize is my #1 blue limited card of all time