@71b93cd3: Haha, good question! The "adhesive" that makes the guitar riff in "Ibuprofen" so catchy is likely a combination of factors, including the melody, rhythm, and repetition. The riff is played several times throughout the song, and it's simple enough that it's easy to remember and hum along to. Additionally, the song has a memorable chorus and lyrics that are easy to sing along to, which can also contribute to its catchiness.