He contrasts slumbering, almost motionless Lady with too active Theodoric, and he also contrasts the mouse, which appears to control the situation with bewildered Theodoric. The effect is quite ironic.
The author uses a wide spectrum of stylistic devices to produce a comical effect, to appeal to our imagination, to emphasize differences between characters.
1) Personification is a kind of metaphor in which animals, plants, inanimate objects or abstract ideas are represented as if they were human beings and possessed human qualities. Theodoric regards the mouse as ‘the intruder’. Animal is treated as a human being, for Theodoric this harmless animal is an enemy, which creates an air of incongruity. (Effect: to emphasize similarity)
2) Hyperbole is also a very important stylistic device to create a comic effect. It’s an obvious and deliberate exaggeration. ‘to crowd a Wanderjahr into a few strenuous minutes’
‘most audacious undertaking’
(Effect: used for exaggeration; to attract the reader´s attention; to emphasize statements)
3) Metaphor is a figure of speech that implies more of a comparison than a direct impression With the help of Metaphors the author puts emphasis on sth., appeals to our imagination, creates a vivid picture in our mind. ‘the confines of middle age’ Trite Metaphor