The following URL returns the five oldest YouTube videos, the oldest of which is Me at the zoo.
Breakdown of URL Request Parameters
Site Specification
q=site:youtube.com
Limit search results (i.e. query) to the specified collection (i.e. the youtube.com website).
Time Specification
&tbs=sbd:1,cdr:1,cd_min:4/23/2005,cd_max:6/23/2005
Time-based search (tbs) using a custom data range (cdr) that is sorted by date (sbd) with a date range starting with the date of the first YouTube video (cd_min), titled Me at the zoo which was uploaded on April 23, 2005.
Type Specification
&tbm=vid
Display video results only.