Tales From the Weird World.

Okay, it goes without saying that all these Tales have h.e.l.p.! in them. Series names to the left of the title note which series a Tale is crossed with (if any). "Crossover" denotes a Tale that has so many different series that we don't want to list them all.

Timeline of the Tales

Blue Jeans

[FY/YYH] Enter, Jean Gets a Promotion, Valerie Gets a Job - fanart
[DB] Father
Touga's Secret - story art
[YYH] Peeping God
[YYH] Potty Animal
[FY] The Seven Weird Seishi

The Lady of Unsanity

[crossover] A Midsummer Afternoon's Dream
[SM] For the Love of the Game

M.E.
(Magnificent Entity)

[Slayers] Education Celebration - takes place on the QoS's Gourrigan's Island
Friend
[YYH] Project K
[YYH] Spatulas and Sugar - story art
Tiles - story art
[traditional] Pledge of Cooperation - parody pledge

the MPF
(the Merry Poppy Field)

Ai Shiteru
Kidnapped!
Spring Fest

Rapunzel

[Slayers/YYH] Is Mandy Jealous?
[HMS Pinafore] The Goddess of the Weird World - parody song
[YYH] The Loch Ness Monster (with parenthetical notes by the M.P.F.)
[YYH] Revenge of the Merry Poppy Field
[crossover] Ribbit
[YYH] St. Patrick's Day
[YYH] Scaredy Cat
[YYH] Valerie's Test
[Wolf's Rain] Weird! - parody song

Hazewriter

[Slayers] Revenge - sequel to Education Celebration

Co-Tales
Blue Jeans
M.E.
the MPF
Rapunzel

[FY/YYH] Wailing Chiriko - by Blue Jeans & M.E.
[YYH] Shining Cat - by Blue Jeans & M.E.; fanart
[traditional] The Weird World Anthem - by Blue Jeans & Rapunzel (parody song)