Does this seem real coming from him?

A guy at work who likes to joke around with me, saying I’m his favorite person; and calling my name all the time, started telling me yesterday that he loves me. His tone of voice changed from simply joking around. Another coworker who overheard him, said “I knew it!”. I try to act jokingly with him, and not let him think I take him serious in anything he says or does. He always does things for me at work, even if I boss him around.