As someone who is 4'9", I cannot tell you how many times I have been called fun-sized. As a child, I would get T-shirts that advertised how fun it is to be “fun sized,” but let me tell you, it isn’t all unicorns and rainbows.
For one, when has fun-sized ever been a positive reference? For example, if you get a fun-sized Snickers, you’re not going to be happy. It is a cop out trying to trick you into thinking that having less candy is good. It isn’t. You are always going to want more candy because it is delicious, and there is nothing fun about running out of candy because it is "fun sized." More like "betrayal sized."
Also, how do you define what heights are fun sized? I have had people who are 5'4" stand next to me and call themselves fun sized. To me, that is tall, so if that is the height for fun sized, what does that make me? Cue the inner crisis of trying to define if I am fun sized.
Another thing is that being short is like 85 percent not fun. I can’t buy anything that covers my lower body without getting it tailored. When I get hugs, my face is always in the sweatiest part of their bodies (read: stomachs or boobs). Even worse, I am always leaned on. Like, seriously, I am not your arm rest; that was only funny the first 100 times.
It isn’t always bad to be short. I will relent, but I think that being called fun sized can make short people like me feel jaded, or ignored, because we face a lot of daily struggles that average sized people never have to think about. Some people might be okay with being called fun sized, but I feel it is condescending; it makes me want to go around calling people boring-sized.
So, think about that before you use fun-sized to describe someone shorter than you. It can be taken as an insult. There are so many great words to call someone who is short -- like perfect, petite or pint-sized. The latter is my favorite because who doesn’t love a pint of ice cream?