Whats the difference between Hideous Laughter and Tasha's Hideous Laughter?

As far as I can tell, it's just duplicated so that you can find "Tasha's Hideous Laughter" under 'H'.

Line for line, they're precisely the same.

The name "Tasha" is copyrighted by WotC, so they published an alternate-title with the name removed, which you can find in a lot of SRD-based content. They probably list it both ways so people looking for one or the other don't inexplicably find nothing.

Apparently it is some weird copyright thing

My strategy, in case anyone thinks it's wrong:

• At the start of combat, cast this on the most dangerous enemy
• Kill everyone else as a team, obviously avoiding any spells that would cancel concentration
• This person is still laughing
• Grab them for interrogation if desired
• If we want to kill them: 
  • Do a round where everyone readies their action as an attack on the subject triggered by the last person before the laughing creature's turn
  • That last person attacks, triggering the saving roll with advantage
  • Immediately the whole party unloads their attacks 
  • Even if the person makes their save, they are already dead or almost dead, and still have to wait another round to take an action. 

Correct me if I'm wrong that everyone could ready an action so that all the attacks unload at once. Seems like a great way to deal with a boss fight. 

EDIT: I realized that there’s an important limitation: I as the warlock can’t ready a spell, because of course I need to maintain concentration on the laughter, so the best thing to do would be to have as many people as possible ready their attacks (to trigger on the person stopping laughing) before my turn, then have me attack while still concentrating, and unload their reactions only when/if the person stops laughing. 

I guess there might be some math to do based on initiative order and stuff, but that’s the gist. Everyone readies attacks based on the person stopping laughing (but while they are still prone), and i as the warlock get an attack in if possible while the target is still prone. 

How do we get the tiny tarts?  

Depends on the DM.

Since it isn't consumed by the spell it could be argued that it is part of your component pouch or rendered unnecessary by an arcane focus.

Quote from jerclarke >>

My strategy, in case anyone thinks it's wrong:

• At the start of combat, cast this on the most dangerous enemy
• Kill everyone else as a team, obviously avoiding any spells that would cancel concentration
• This person is still laughing
• Grab them for interrogation if desired
• If we want to kill them: 
  • Do a round where everyone readies their action as an attack on the subject triggered by the last person before the laughing creature's turn
  • That last person attacks, triggering the saving roll with advantage
  • Immediately the whole party unloads their attacks 
  • Even if the person makes their save, they are already dead or almost dead, and still have to wait another round to take an action. 

Correct me if I'm wrong that everyone could ready an action so that all the attacks unload at once. Seems like a great way to deal with a boss fight. 

EDIT: I realized that there’s an important limitation: I as the warlock can’t ready a spell, because of course I need to maintain concentration on the laughter, so the best thing to do would be to have as many people as possible ready their attacks (to trigger on the person stopping laughing) before my turn, then have me attack while still concentrating, and unload their reactions only when/if the person stops laughing. 

I guess there might be some math to do based on initiative order and stuff, but that’s the gist. Everyone readies attacks based on the person stopping laughing (but while they are still prone), and i as the warlock get an attack in if possible while the target is still prone. 

 By the time this is better than Sleep, for what you are proposing, you'd be better served by casting Suggestion. This spell is a corner case for creatures that aren't affected by sleep or charm.

Also, it is easy entry for the goolock capstone. Make them laugh, help them back up, and you have gained a permanent thrall. 

Stop giving the spells different names, or make it possible to turn off. Please. I don’t want this nonexistent spell to keep popping up whenever I try to look at a list of spells.

nothing

what's the feather in matereal for? what about the tarts?

Quote from coccorc >>

what's the feather in matereal for? what about the tarts?

 They're for casting the spell.

Did this not have a level escalator in the past to target an additional creature for every slot above first?

Am I a time traveler? Has the overuse of this spell by my NPCs caused permanent psychic damage to the DM?

According to Lore,  You usually get the tarts by stealing them from the Queen of Hearts...

If a spell caster has war caster and very good constitution saving throws, this is a great way to disrupt their concentration on a spell.  This might be more useful for DMs than for players in that regard...

What the Difference between Hideous Laughter and Tasha's Hideous Laughter??????

This is the golden spell when it comes to GOOs.

Not only does it deal damage, but it is one of the only spells in the game that invokes the incapacitated. Pair this with Create Thrall, and casting this spell is an almost instant way to instantly get someone charmed and under your control.

So I need some Pop Tarts. Got it.