Throwaways ECs Should I put them on my application?Answered
Is putting I wrote a short story (which I just wrote for fun) worth the space on app just to add more ECs to my list
It really depends on the situation. On the Common App, you have space for up to 10 extracurricular activities. If you're looking at your current list of ECs and you have fewer than 10 activities on it, it's reasonable to add an entry about writing a short story. However, if you already have 10 ECs on your list, and they are all more impressive than the short story, it's best to leave it off and keep the more impressive ECs. The only case where that logic doesn't hold is if you're applying for majors or programs that are specifically focused on writing/creativity, in which case including the short story (even if it's less impressive than some other ECs) might make sense.
Generally, you just want to include the 10 most impressive extracurricular activities that you've participated in on your Common App (but don't worry if you have less than 10, that's okay too!)