Alternately: Alice grew up to be hideous, and most of the characters can tell...except Bob, who has some sort of facial hair/drool fetish.
Zig Zagged: Bob expected Alice to be beautiful, but she's plain and unnoticeable... but wait! Who's that hot girl Bob just ran into? Is it really Alice? Yes... but she's wearing a lot of makeup. She stops doing so, and she's back to being plain and unnoticeable... but then Bob takes a closer look at her and realizes she's rather cute after all. (And just to seal the deal, a school dance comes along and She Cleans Up Nicely.)
Averted: Alice didn't change much in terms of looks.
"We need to make Alice and Bob's reunion a bit more dramatic. Maybe Bob finds her really attractive now?"
"Bob knew Alice before she was pretty, so that the viewers know that he's not shallow, but we don't want anyone ugly in the role.
Lampshaded: Bob meets up with the now beautiful Alice after ten years and says, "You know, I always knew you were going to grow up hot."
Exploited: Alice, a very plain young girl, decides to wait until she's older and hopefully more attractive to woo her crush.
Defied: Alice uses clothing and makeup to downplay her looks.
"Maybe this blind date with Alice won't be so bad after all. She probably grew up really hot."
"I know we remember Alice as a dorky girl, but that was ten years ago. There's a good chance she'll be much prettier when we see her again."
Conversed: "Is this gonna be another anime where he meets a hot girl, then finds out it was his childhood friend?"
Implied: Bob says that he is waiting for "some kid" he knows and makes a Spit Take when Alice enters the room and identifies herself.
Deconstructed: We see that Alice spent years of her life on plastic surgery and other measures to become pretty for her "return," but the experience leaves her hollow and unfulfilled after all.
We see that Alice spent years of her life on plastic surgery and other measures to become pretty for her "return," but the experience leaves her hollow and unfulfilled after all. However, Bob falls in love with the person behind all that plastic surgery, which helps Alice recover and feel better about who she is now.
We see that Alice spent years of her life being fit and healthy as well as undergoing Character Development. She also had friends and loved ones to support her, and she learns tips on becoming pretty the safe, yet efficient way. By the time Bob returns, he finds Alice dazzling, even when she forgot to put makeup on that day.
Played For Laughs: Bob is comically speechless after seeing the new stunning Alice.
Played For Drama: Bob is Alice's Disappeared Dad and missed most of her life while he was away.
Well, that's a nice looking trope, and...wait, was that She Is All Grown Up? I haven't seen her since grade school! Wow...