Light Yagami/Harry Potter
Light swallowed his rising panic and turned his head, staring at the birthday boy instead. Dudley Dursley was turning three and Vernon had taken that chance to invite everyone from his work to his home. A bid for a promotion. Light knew those. Soichiro Yagami was Chief at NPA and later Deputy Director. He had seen his father invited at plenty of those.
Dudley was, to put it mildly, over healthy. Excessively so. Light wondered if Petunia knew she was setting her son up as a high risk obesity and heart attack patient. And then promptly decided it didn't matter. She fed her son too much and fed Light 'comparatively' little. 'Comparatively' meaning enough for a normal, healthy child of 35 months old.
Light didn't know whether to curse her or thank her for it. He chewed on his cake, too sweet by far, too much icing, and decided on neither.
Two life-times in and Light still didn't know what L saw in cake.