These magnet straws came with the Slurpee/Squishee cups, in 7/11 stores (done up to look like the Kwik-E-Mart) to promote The Simpsons Movie. The characters are held on with magnets, and can be removed from the straws.
This set of cups was sold in 7/11 stores, done up to look like the Kwik-E-Mart, in 2007 to promote The Simpsons Movie, along with a set of magnet straws. Far as I know, they were only released in the US. All have the Squishee, Slurpee, and 7/11 logos on the back (bottom right)