13 of 20 added nougat, added pictures

Eldarerathis summarized it very well. To add some things: The 1.1 version was internally called Petit Four by Google, and that's how it all began. Google is installing a giant pastry on their lawn at Mountain View each time a new version is about to be launched.

You can see pictures of that display at different stages here:

Overall display (Cupcake to Eclair, with Nexus One) http://farm5.static.flickr.com/4030/4453391412_8ec6dfa2a8_o.jpg Donut, Android logo, Nexus one, Cupcake, Eclair

Honeycomb http://eurodroid.com/pics/honeycomb_statue-1.jpgHoneycomb

Eclair, Froyo, Gingerbread, Honeycomb and Ice Cream Sandwich http://www.androidguys.com/wp-content/uploads/2011/10/ice_cream_googleplex.jpg Froyo, Gingerbread, Icecream Sandwich

Gingerbread, Honeycomb, Ice Cream Sandwich and Jelly Bean http://s1.uswitchstatic.com/_img/library/news_image/android_jelly_bean_sculpture_at_googleplex_520x300x24_fill.jpg

Gingerbread, Icecream Sandwich, Jelly Bean

Kit-Kat http://www.droid-life.com/wp-content/uploads/2013/09/kitkat-android-650x433.jpg KitKat

Lollipop http://www.androidcentral.com/sites/androidcentral.com/files/styles/large_wm_brw/public/article_images/2014/10/lollipop-statue-1.jpg?itok=Ikh29MXd Lollipop

Marshmallow http://www.androidcentral.com/sites/androidcentral.com/files/styles/w400h225crop/public/article_images/2015/12/android-marshmallow-4_0.jpg?itok=GsKySY9O Marshmallow

Nougat http://www.androidcentral.com/sites/androidcentral.com/files/styles/xlarge_wm_brw/public/article_images/2016/06/android-nougat-statue-8.jpg Nougat