Two of these in spoilers because it's too much:
Mousewhisker-
He used to be a more brash apprentice back in his earlier days, as shown by the whole squirrel incident with Cinderheart. Overtime, he mellowed out and became the warrior he is today. He used to be jealous of his brother, as his brother was able to catch the attention of she-cats when he couldn't catch a mesely squirrel; he hated that his brother got more attention than him, and eventually just gave up on trying. He probably had a crush on Honeyfern or Poppyfrost. Mousewhisker used to have a crush on Minnowtail, but quickly left it behind as Minnowtail didn't feel the same way and it was a brief infatuation anyways. It never went any further than that. He slowly began developing feelings for Hollyleaf, and was heart-broken when she "died". He joined the Dark Forest out of jealousy of Berrynose, and manipulation on Hollyleaf's death, the DF cats saying it was his fault that she died and that Berrynose wouldn't let Hollyleaf die.
Hazeltail-
She was an average apprentice back then, with her trying to fit in with her fellow Clanmates as well as her family. However, she never saw a reason to be ashamed of her heritage- as shown by The Sight. Hazeltail was rather excitable, and would never shut up if presented the opportunity to speak about something. As she and her brothers grew up, she was the only remaining link between the two- especially during Omen of the Stars. She also had a brief crush on Hollyleaf, but knew that her brother liked her, so she never spoke up about it as she knew how he felt since Berrynose. She was generally caring about her Clanmates, and was sort of the "mom friend", if you will to some of her closest.
Toadstep-
He likely had a crush on Lionblaze, and would always try to be like him. He was brash and snappish, but ultimately had a good heart. Toadstep was always jealous of Cinderheart, as he saw the way that they looked at each other.
Rosepetal-
She used to have a crush on both Foxleap and Bumblestripe, however, her crushes on both of them lasted relatively short. With Bumble, she couldn't see why Dovewing didn't like him in that way and would constantly make it her duty to get them together. Of course, when they broke up Rosepetal was reasonably confused. Also, a more spoiler-y bit:
As shown in LS, she mentions that she had a cat she once loved too. Since the editors likely forgot about the plans to make Rose x Fox canon and everyone has been assuming it was Bumblestripe, for the sake of this, I'm headcanoning that it was Bumblestripe who she crushed on, but didn't feel the same.
