It doesn’t demand to be taken seriously, however *'The Gnome-Mobile'* manages to be charming and funny. Walter Brennan is easily the strongest element, delivering a double performance. He portrays Mulrooney with warmth and kindness, while also embodying Knobby’s grumpy and irritated demeanor. I didn’t even recognize it was him playing both parts for quite some time, if not for the opening titles. The other perform…