9 of 20 added 5 characters in body

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

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

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

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

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