Purveyors of April Foolery, Blizzard, have temporarily added a giant head mode to Heroes of the Storm.
"Variety is the spice of life in Heroes of the Storm, and we’re always looking for new ways to allow players to customize their Heroes and infuse their personalities into the denizens of the Nexus," they say. "Big Head Mode is just another step in that direction."
I think perhaps I'm not very good at observing heads because, although obvious on the menu screens and when you scroll wheel to zoom in, the default aerial view doesn't seem very different to me.
The mode only activates when you load in to a match so you won't see it immediately on the menu screens. Scrolled in it's more obvious and I must admit I didn't realise I'd respawned because I was too busy staring at chibi Tyrande and trying to decide if the mode was ultimately something I liked.
From the request for feedback from players I wouldn't be surprised if Blizzard was trying to work out whether to keep the mode, either as a toggle or an unlock as the game progresses. If that's the case: it really doesn't do anything for me, but then I am a joyless jerk.