"Et tu, Brute? Then fall, Caesar!," e.g

• Word in a comic balloon, perhaps
• "Oh no, a spider!"
• Cry of alarm
• ____ a mouse!
• ''A mouse!''
• Musophobe's shout
• 'It's a mouse!'
• What a mouse may evoke
• Squeal of surprise

Wiktionary Word definitions in Wiktionary
interj. 1 Representing a scream or shriek (especially in comic strips and books). 2 Expressing (sometimes mock) fear or surprise. 3 The shrill vocal sound of a mouse, rat, or monkey. vb. To produce a high-pitched squeal, as in fear or trepidation.