***I had taken an unworthy hiatus for SUCH a long time. Apologies for that. But I'm back now, and I will continue the list of things NOT to do in YGO! I'm also doing one for some more genres too.
Anyway, without further ado, let's get back to it. Credit to the great Angel-of-Anime Mizumi and the great yukimoto1 for MORE ideas!
WARNING: May contain Undertale, Hetalia, or any other things not keen to any eye.***
201) Show Haou Darkshipping
202) Post dank memes in Yusei's apartment
203) Let Yami make his own version of "Do You Want to Bulid a Snowman" from Frozen.
-He will sing "Do you want to Duel me" instead, pretty badly
204) Show ANYONE in the cast Undertale
205) Give Sans/Papyrus a Zombie deck
206) Allow any of the Yami characters to have a bad time
-It's a beautiful day outside.
207) Ask Italy to duel Yugi
-I bet all his cards would contain white flags in them.
208) Use the Mermail characters as sashimi
-(I am both sorry and not sorry)
209) drop Yugo in the Fusion dimension
210) Call Yugi a baby panda
211) Call the girls from Duel Monsters, GX, and 5DS (with the exception of those below 15 and above 40) bimbos due to…huge knockers
-I'm sorry, Senpai!
212) Say "FRIENDSHIP SUCKS!" to Tea
213) Rub off the happy face Tea drew on Yugi, Tristan, and Joey
214) Give Joey a Western accent
215) Give Joey an Australian accent
216) Give Joey an Asian accent
-You can thank me for scarring y'all for life later.
217) Let the Annoying Dog loose in any of the worlds
218) Jump onto one of the mountable monsters during a duel
-It sounds fun to do. But…Wait. They're holograms. Whoops.
219) Invite any of the YGO characters to their fan clubs
-HA! I laughed so hard when I saw this. Thank you sooo much for saying this one.
220) Send Yubel into space
-…again
221) Let any of the YGO characters read the love fanfics
-I think I mentioned this. The AU and One-shots
222) Show all the cast bondage hentai
223) Put the characters in Hope's Peak Academy
224) Or the Neo World Program
225) Or Towa City
226) Not turning Yugi into a merman in a H2O just add water & YGO crossover
-otherwise it will not be funny
227) Send the characters to Yokai Academy
228) Send Vector/Yami Marik (Melvin) to Wonderland
229) Get Tristan into vlogging as a monkey
230) Call Tristan "banana brain" for that matter.
231) Insult Marik's half-shirts
232) Make no comment
233) No comment
-HA! So there.
234) Give Zane an Electric type Pokemon
235) Give Cyrus Morphtronics
236) Tell Yami Bakura NOT to steal
-but…
237) Immediately steal from him
238) Run the Millennium Item Service Company
239) Show Tristan a ghost
240) Play the tape that tells you that you'll die in 7 days
241) Turn all of the cast into magical girls
242) Let the cast play 8-Player Smash
243) Let the best of friends in the whole character roll play Mario Party 10
244) Dye all the Millennium Items pink
245) Let Dartz and his crew share "wankings" (rankings)
246) Mock Kaiba in front of his own house
-or company (It would be hilarious though, so "Enter at your own Risk.")
247) Lock the villains in a room playing "Barbie Girl" non-stop
248) Grope the females
-EW! I'm sorry!
249) Hijack Jack's D-Runner and shout "Card games on MOTORCYCLES~" next to him
250) Place the protagonists against Allen Walker from D Gray-man in a game of poker
***Got a lot more ideas from this! Thanks for the support, and I hope I'll be able to finish off strong! Until then~!***