The first level of PR2

[Master Raiden]

-_- lol by Sonic (190) is the oldest published level, but there are some even older unpublished levels that still exist:

2 by DKundertaker (110) (User ID = 3925)
ello by Runescape (159) (User ID = 134)
chimpy's extra annoying madness by CHIMPY (163) (User ID = 31)
chimpy's evil by CHIMPY (176) (User ID = 31)
Running life by <unknown> (180) (User ID = 1247)
goal rush by <unknown> (181) (User ID = 1247)
ultmated race by <unknown> (182) (User ID = 1247)
Skillz' poof by skillz (183) (User ID = 123)
vanish madness by CHIMPY (184) (User ID = 31)
Age of speed by <unknown> (185) (User ID = 1247)
Skillz' Boomshakalaka! by skillz (188) (User ID = 123)

I can't seem to find User 1247 anymore, but their levels still exist somehow.