Is my boyfriend gay, i'm really worried!?

I would say he is possibly Bi curious. Favorite Color means nothing by the way. It isn'tt uncommon for couples to imagine someone else in bed. Although calling out Bart is rather alarming. My advice would be to ask him in a non judgmental way. If he feels comfortable enough with you at the time you may get a straight answer out of him. Just bring all these points up and let him know you have a right to know. i hope this helps you :)