It appears when its stats lower and if youre talking about lets go when its xs.
Edit: not sure with go but probably not important. Also in Pokemon smd [super mystery dungeon] it happens when a Pokemon awakens.
And you don't need to point out youre a girl people just use "he" as "you". Also I only check the gender page on people i'm friends with. Or have cool profile names and pictures.
Edit 5 seconds later: Also you can't act like its my fault I just checked youre profile you did not say youre gender so don't act bratty :[
More edits: Just googled it and it will have one if you caught it within the past 24 hours source Also if I have to copy/paste the words can someone help me get the green thing around it and find the right piece to copy/paste so can someone do that thxs?