Rust, 116 bytes

use rand::Rng;let f=||"abcdefghijklmnopqrstuvwxyz".chars().collect::<Vec<_>>()[rand::thread_rng().gen_range(0..26)];

Rust Playground

Rust, 116 96 bytes

use rand::Rng;let f=||b"abcdefghijklmnopqrstuvwxyz"[rand::thread_rng().gen_range(0..26)]as char;

Rust, 320 309 bytes

use rand::Rng;let f=||["Yup","You doubt me?","Of course","... did I miss something?","please send teh coffee","Watching this endless list of new questions never gets boring","Kinda sorta","You should totally drop that and use jQuery","¯\\_(ツ)_/¯","... good question"][rand::thread_rng().gen_range(0..10)];

Rust Playground

Rust, 116 bytes

use rand::Rng;let f=||"abcdefghijklmnopqrstuvwxyz".chars().collect::<Vec<_>>()[rand::thread_rng().gen_range(0..26)];

Rust Playground