It was featured in the movie My Girl.
Here's the script part of it.
Vada backs off, followed by Shelly
THE TWO MEN THAT GOT OUT OF THE CAR ARE PROCEEDING UP THE SULTENFUSS' DRIVEWAY
FOCUS ON PHIL, HARRY, VADA, SHELLY AND GRAMMOO AT THE TABLE OUTSIDE, SHELLY SAYS A SEMI-GRACE
SHELLY
Rub a dub dub, thanks for the grub, yay God.
HARRY
I'll second that.
The phrase was also heard in the the Season 2 Episode 18 of Family Guy. Watch video here.
Of interest, THR asked its entertainment industry readers to vote on the most memorable quote from every movie ever made. Find out what topped the list at HollywoodReporter.com.