回复：趁着足球中场休息。想来探讨下。甜瓜怎么面瓜了？

It is because his name! Carmelo  ... in US, only great athelet deserved to be called by initials, like KG, TD, CP3. Back in Syracuse, fans call Anothony Melo, plus he got a very sweet smile.  Then chinese reporter translate Melo to 甜瓜, then somehow became 面瓜.
The way he play, nothing related to 面瓜.
He is one of the best from Syracuse!