I Think That Possibly Maybe I'm Falling for You

"For all Penny knew, she and Andrew were close friends who she occasionally had spats and arguments with. Sometimes, Andrew was glad that Seaweed Brain remained oblivious to his true feelings for her. Other times, he was frustrated with how stupid this girl made him feel - especially when she came back to Camp Half-Blood the summer before the Second Titan War." Percabeth One-Shot.