On Vashon Island (near Seattle, Washington), a tree grows carrying a rather unusual passenger - an old bike. Apparently some kid chained a bike to the tree decades ago and never picked it up, leaving the tree no choice but to grow around the bike.
The tree and island gained some level of notoriety when Berkeley Breathed, creator of Bloom County, wrote a children's book inspired by the bicycle eating tree entitled Red Ranger Came Calling.
Story found via The Museum of Hoaxes (but this was not a hoax), pic via Arborsmith.
http://www.roadsideamerica.com/tips/getAttraction.php3?tip_AttractionNo==1412
If this is real, it was obviously set up a long, long time ago, and never touched since. Dubious, but not impossible.