The relationship between "I scream" and "ice cream" called an "oronym" - a phrase or word that sounds like another phrase (a "homonym" is a single word that sounds like another single word). Examples would be: four candles; fork handles euthanasia; youth in Asia realize; real eyes The meanings of the different phrases or words have no relationship at all to each other - they just sound alike.

They just sound the same - there is nothing special other than that except famous song "I scream, you scream, we all scream for ice cream" (I've never been able to use that bit of arcana before - cheers!)