Apathic? That's not a word, my good sir. If you meant apathetic, then yes, being serious would in essence mean lacking emotion. As far as it looking like a mental patient, erm, most mental patients are quite lively. It would most closely resemble someone with a damn good poker face or a zombie.
Or a zombie with a damn good poker face.
And learn your French a bit more accurately. "It's 'the' impossible" isn't exactly grammatically fluent.
Lol see what I did thar? I r closely pick over small mistakes and bring them out so I r felter superior lol. Lol.