I have had many discussions with Muslims about whether or not having a crush is haram, and have heard all sorts of opinions. But I think we can safely say that it is not haram since you have little control over your feelings; what you do about it on the other hand, may well be...
.Abu Hurayah reported that Allah's Messenger (S) said:
"A son of Adam's share of zina has been predestined for him, and he will inevitably fulfill that. Thus the eyes commit zina by looking, the ears commit zina by listening, the tongue commits zina by speaking, the mouth commits zina by talking/kissing, the hands commits zina by acting (or touching) the foot commits zina by walking (toward the sin) the soul wishes and desires and the private part confirms all of that"
[Bukhari and Muslim]
According to this hadith, zina, to some extent is inevitable for man. Islam has told us that the best way to control zina of the heart is to lower the gaze.. prevention being better than cure and all that..
"Tell the believing men to lower their gaze (from looking at forbidden things), and protect their private parts (from illegal sexual acts, etc.). That is purer for them. Verily, Allah is All-Aware of what they do.
And tell the believing women to lower their gaze (from looking at forbidden things), and protect their private parts (from illegal sexual acts, etc).
[Qur'aan, 24: 30-31]
Simple problem, simple solution. But who really does it?