Here's the reason (if ever a reason there was) to learn how to play a ukulele. According to Muppet Wiki:
"Rubber Duckie" is Ernie's signature song, a tribute to his beloved Rubber Duckie. The song enjoyed popular fame, reaching number 16 on Billboard's "Hot 100 Singles" chart in 1970.  It was even nominated for a Grammy Award for Best Recording for Children, but it lost to The Sesame Street Book & Record, which, ironically, also contains the song.
WARNING: This song is highly contagious. Tune may be stuck in your head for days.
Sesame Street Ernie sings "Rubber Duckie"
This song can work really well on a ukulele if done right. There are many YouTube videos of those that have tried. Here are two that don't suck:
You can find a few song chords to try out below:
For a Jazzier swing, try this one:
Note: Capo the 1st fret to play in the original key.
I don't actually like any of these exclusively so this is my mashed-up chords version:
Rubber Duckie - Sesame Street Ernie