Can a Mouse ride in a Heli ?
Yes, of course, most helicopters are large enough. Even most RC-models can do it. But not all ! Here you see the low end of those high-tec-maschines: (M?)TOW =6.9 gr = less then 1/4 oz = less than 22 Aspirins! Including a filled up tank, - which is here a 45 mAh battery. And that weight includes 2 engines, gears, all the rotors, the frame, the IR-remote control. 
See more details- and even a flight- on the webpage of Pixelito.