Involuntary musical imagery (INMI or "earworms")- the spontaneous recall and repeating of a tune in one's mind-can be attributed to a wide range of triggers, including memory associations and recent musical exposure. The present study examined whether a song's popularity and melodic features might also help to explain whether it becomes INMI, using a dataset of tunes that were named as INMI by 3,000 survey participants. It was found that songs that had achieved greater success and more recent runs in the U.K. music charts were reported more frequently as INMI. A set of 100 of these frequently named INMI tunes was then matched to 100 tunes never named as INMI by the survey participants, in terms of popularity and song style. These 2 groups of tunes were compared using 83 statistical summary and corpus-based melodic features and automated classification techniques. INMI tunes were found to have more common global melodic contours and less common average gradients between melodic turning points than non-INMI tunes, in relation to a large pop music corpus. INMI tunes also displayed faster average tempi than non-INMI tunes. Results are discussed in relation to literature on INMI, musical memory, and melodic "catchiness.".