puppy love

Fig. mild infatuation; infatuation as in a crush. (Used especially of adolescent relationships.) Is it really love or just puppy love? Look at them together. It may be puppy love, but it looks wonderful.

romantic love which a young person feels for someone and which usually disappears as they become older At the time I was sure I would marry him when I grew up but of course it was just puppy love.

Also, calf love. Adolescent love or infatuation, especially one that is not expected to last, as in Beth is besotted with him, but we think it's just puppy love, or He's got a bad case of calf love. [First half of 1800s]

A juvenile crush, an infatuation. The phrase refers to an adolescent male's total devotion to the object of his affection by displaying the uncritical ardor of a young dog to its owner. “Mooning over” and “calf eyes” are apt phrases for such an affliction. The 1960s teen singing idol Neil Sedaka had a hit record of a song by that name.