Tia is a Pug, American bulldog cross.
Although her resting expression makes her look a little worried, she clearly had a great time running about with her pal Rupert and a tennis ball.
That was until, Rupert took the tennis ball from her mouth mid chase. Her expression changed at that point and her disgust at his behaviour was obvious to all. They didn't fall out for long though and she let him have the ball in the end.