There is a statement in the closing credits: "No slugs were a-salted in the making of this film." The joke is that salt is deadly to slugs.
There is a scene in the closing credits: Roddy's owners return to their apartment with a pet cat, to Sid's horror.
Then the Tom Jones song "What's New Pussycat?" plays over the closing credits.
During the closing credits, slugs crawl on and off screen, interacting with the credit text.