In anime, peachification, in Japanese Piichi-hime-ka ピーチ姫化, literally "Princess Peach-fication," is the term for turning characters into Princess Peach-like characters by putting a Super Crown on them. It's also spelled peachfication or peach-fication.
See Bowsette and Other Princesses for reference.
In Japanese, iteration marks are symbols which can be used to repeat parts of a word. The most common mark, 々, is written instead of a repeated kanji. The marks ゝゞヽヾ are written instead of a repeated kana. Besides those, there's also a long く mark, this thing 〻, and the ditto mark 〃.
In Japanese, the ditto mark (〃), called nono-ji-ten ノノ字点, because it resembles the katakana ノ twice, tenten てんてん, chonchon ちょんちょん, and officially onajiku kigou 同じく記号, works just like the English ditto mark: it's used when a part of one line is the same thing as the previous line.
The only difference being that English uses a ditto mark for each word repeated, while Japanese uses just one ditto mark for the entire repeated part.
This mark is unlikely to show up in manga, or in any dialogue text. It can show up in a school, an actual, real school, in class, when a teacher is writing on an actual blackboard, as well as in tables when you have multiple rows and cells of a row are the same thing as cells of the row above.
In Japanese, the symbols ゝゞヽヾ are iteration marks for kana (hiragana and katakana). They work just like 々 works for kanji, by repeating the character that precedes them, except that, while 々 is commonly used, ゝゞヽヾ are rarely used in modern Japanese.
Note: if you saw ヽ in the furigana space, that's probably an emphasis mark instead.
The differences between the five symbols are pretty simple:
The symbols ゝゞヽヾ are called ichi-no-ji-ten 一の字点, "character mark [that looks like] 一," but they're also known by the same names 々 has: kurikaeshi 繰り返し, odoriji 踊り字, etc.
In Japanese, the small katakana ke ケ, ヶ, is a bit different from the other small kana, in that it's not usually read ke, but instead as ka か, ga が, or even ko こ. Similar to how the small tsu っ isn't read as tsu つ.
For example, ni-ka-getsu 二ヶ月 is how you say "two months," as in counting the months. It's not read ni-ke-getsu despite having a ke in the middle.