The Collaborative International Dictionary of English v.0.48:

itsy-bitsy \it"sy-bit"sy\, itty-bitty \it"ty-bit"ty\, a.
   very small; tiny.

   Syn: bitty, bittie, teensy, teentsy, teeny, wee, weeny,
        weensy, teensy-weensy.
        [WordNet 1.5 + PJC]

              It was an itsy-bitsy teeny-weeny yellow polka-dot
              bikini
              that she wore for the first time today. --Song
                                                  lyrics
        [PJC]

WordNet (r) 3.0 (2006):

itty-bitty
    adj 1: (used informally) very small; "a wee tot" [syn: bitty,
           bittie, teensy, teentsy, teeny, wee, weeny,
           weensy, teensy-weensy, teeny-weeny, itty-bitty,
           itsy-bitsy]