The first time it happened Donna was completely innocent. When she'd looked up from her lollipop and seen the Doctor's face, she knew exactly why he wasn't hopping around as usual. She was kind and said nothing. Since then, however, her inner "Evil Donna" had been having way too much fun with him. She liked the attention, and the Doctor was rather cute when he got flustered.
Now she sat in a very low-cut top, leaning unnecessarily far over her book, biting her lip in concentration... or just to draw attention to her mouth. The Doctor hadn't spoken for a while, and he wasn't being nearly as suave as he thought in sneaking glances down her shirt. Finally he cleared his throat. "Wha...what are you reading?" he stuttered, belying his cool tone.
Donna looked up and smiled innocently. "An original copy of Justine by the Marquis de Sade. I picked it up in Paris."
The Doctor coughed so violently, Donna was genuinely concerned for a moment. "Great," he recovered quickly. "Um, excuse me, I just remembered I think I left my mallet in my room." She watched him sprint away, grinning as she eyed the mallet hanging from the console.