Big Budget Beef Up
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When characters suddenly seem much much stronger than before, as an issue of time and money. Noticeably common in movie adapations, but also in OVAs and important episodes given higher budgets. Almost never explained.

To fit a typical episode formula, the heroes may have to spend a certain amount of time fighting a single opponent. However, dramatic episodes may have the heroes fighting hordes of similar minions or critters. To make use of short time, they'll be cutting through them quickly enough you wonder why it wasn't so easy before.

Also very effective the first time, since it shows how cool the whole cast can be in its first real big fight.

Chinese Girl
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A cute ethnically-Chinese girl, usually foreign-born with a variable accent. Nearly guaranteed to appear in a cheongsam at some point. An inordinate amount of them (even for anime) will know martial arts.

Pretty Freeloaders
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Sometimes Unwanted Harems become so common that fans see them everywhere. While a bishoujo series can have one guy and a big female cast, sometimes it's just for the audience's sake. In romantic seinen series, the lead might just be interested in one girl from the outset. Unfortunately, the rest can cause non-romantic trouble rarely doing anything too useful, aside from fixing problems they caused themselves.

Pretty freeloaders typically gain audience sympathy over time, and usually have barely any sort of direct romantic attachment to the main character.