Dress Down! Folks us judges finally have a modern framed card that causes as much headache as an old favorite of all creatures losing ability but being easier as there is no 7b to worry about like Humility

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To tackle this question we go straight to the Oracle Text of Dress Down.
Flash
When Dress Down enters the battlefield, draw a card.
Creatures lose all abilities.
At the beginning of the end step, sacrifice Dress Down.
Wow so much abilities with four in total! The key here is the triggered ability at the end step and the static ability that causes creatures to lose all abilities. Note that the static ability operates in layer 6 as this knowledge is critical in answering the bulk of the scenarios we face.

Scenarios
Pitch to Grief You

If Dress Down is in play before Grief or any of its fellow MH2 elemental incarnates ETBs, its ETB trigger will not trigger. Ditto if Grief is evoked and Dress Down is in play before Grief resolves, its controller do not need to sacrifice Grief to its evoke trigger.
Sometimes the player lets Grief resolve before casting Dress Down, that way both ETBs are already on the stack so the discard and evoke sacrifice still happens.

Dressing Death

My personal favourite, Dress Down will make the Shadow 13/13. Tarmogoyf is a 0/1 and Scourge of the Skyclaves dies as a 0/0.

Moon Cares Not for Dressings

Magus of the Moon operates on Layer 4 while Dress Down losing abilities operates on Layer 6. We apply layers from 1 to 7 in order so the Magus still Moons the nonbasic lands despite being Dressed Down.

The Ilysian Grove

Similar to Magus of the Moon, Dryad’s ability affecting lands to be every basic land type applies on Layer 4 which is applied first before Dress Down removes it in Layer 6. Hence all lands you control are of all basic land type. However the ability to play an additional land each turn is removed.

Karnstruct Likes Their Clothes Thank You

The Karnstruct tokens will lose their ability with Dress Down in play rendering them 0/0s and be placed in the graveyard after state based actions are checked.

Morphing Cloaked Disguise Manifesto

When Dress Down is in play all the face down creature cards are generic 2/2s with no abilities. You cannot turn the creatures face up via its Morph/Megamorph nor Disguise cost as the creatures do not have those abilities.
You can turn the face down creature cards up even with Dress Down in play if it was Manifested or Cloaked as Dress Down does not remove the mana costs of the creature. The rules of Manifest and Cloak does not let you turn up Manifested or Cloaked non-creature cards.
Note that turning face up is a special action which players cannot respond to as it does not utilise the stack.
However if the card hiding below is a non-creature with Morph, Dress Down does not affect them when you want to turn them face up.
Nyx and Its Denizens

Without sufficient devotion, the Gods remain as they are. The devotion type changing effect applies on Layer 4. If you have or gain sufficient devotion, the God is just a Legendary Enchantment Creature – God with its printed power and toughness with Dress Down in play. If you lose devotion during the turn it was a creature with Dress Down in play, it regains its abilities because you apply Layer 4 before Layer 6.

Opalescence Devastation

One does not skip Opalescence when it comes to such effects. However, compared to Humility it is easier. Opalescence operates on Layer 4 while losing abilities is in layer 6. Dress Down also loses its trigger to self-sacrifice at the end step.
If Opalescence is in play before Dress Down, you will not be able to draw a card.

Static’ed Phyrexian Preators

If Dress Down is in play 1st, then no abilities on the Phyrexian Preators. Similarly if either Sheoldred or Elesh Norn is in play and you cast Dress Down, both Preators will have no effect.
Sheoldred will not be triggered to cause you to lose 2 life from your Dress Down card draw. Elesh Norn will not stop Dress Down from triggering the card draw. Ditto if you are the controller of both the respective Preator and Dress Down.

Wrath of Dreadnoughts

If Dress Down is in play before Uro or Phyrexian Dreadnought resolves, none of the triggers happen.

If Dress Down is only in play after either resolves, the trigger abilities are still on the stack and trigger as per normal.

Blitzing Dash

If you Blitz or Dash a creature, with Dress Down in play regardless of order, the creature will lose all its abilities including the haste granted by Blitz or Dash.

The delayed trigger of sacrificing to Blitz or returning to hand of Dash still triggers regardless. This is because Blitz and Dash have cast triggers and not ETB which is why Dress Down does not affect either.

Manlands

If Dress Down in play when the manland is a creature, it will lose all its printed abilities such as the ability to tap for mana and its ability to activate the manland ability.

If Dress Down in play when the manland is still a land then the manland ability is activated, the ability will grant the manland all the associated abilities due to timestamp order. In Inkmoth’s case a 1/1 Phyrexian Blinkmoth Artifact Creature with Infect and Flying. It will still lose all its printed abilities including the ability to tap for mana and its ability to activate the manland ability once it is a creature.

No Government Car

Dress Down does not affect Unlicensed Hearse as it is an artifact.
However once Unlicensed Hearse is crewed when Dress Down is in play, it is placed into the graveyard as part of state-based actions are checked as it is a 0/0.

Interaction of replacement effects, CR 614.12
To determine which replacement effects apply and how they apply, check the characteristics of the permanent as it would exist on the battlefield, taking into account replacement effects that have already modified how it enters the battlefield.
I have snipped the relevant portion of CR 614.12 which explains the situation for the next subset of interactions below with Dress Down.

Stay Leashed

If Dress Down is in play before they resolve, creatures will not enter play with any counters on them. Cackler stays leashed as a 1/1, Murktide stays a 3/3 and the Ballista is placed into the graveyard as state-based actions are checked as it is a 0/0.

A common play is for players to cast Thing in the Ice with a Dress Down in play for it to ETB with no counters. The Kraken will be unleashed! You still need to cast the instant or sorcery to trigger transform.

No Calling Names

If Dress Down is in play before any of these creatures resolve, you do not get to name a card nor color.

Modulation error 404

Similarly, if Dress Down is in play, all Modular creatures will enter as 0/0 and put into graveyard as state-based actions are checked as no counters will be placed on them.

Existing Modular creatures also will not trigger their Modular ability when they die if Dress Down in play. This is the same for similar effects like Undying.

Scarecrow the Painter

If Dress Down is in play before Painter’s Servant ETB, you do not get to choose a color.
However if Painter’s Servant has already selected a color say Red, then Dress Down is cast. What happens? So back to Layers, Painter’s Servant’s effect applies in Layer 5. So we apply in order, where everything is painted Red then Painter’s Servant loses all its ability due to Dress Down.

Copying Down

If Dress Down is in play while Clone is on the stack, CR 614.12 will apply. Clone will not have its replacement effect and ETB as a 0/0 which will be placed into graveyard as state-based actions are checked.
Clone also does not get to copy anything.

Living Steel

However for Sculpting Steel, it can copy an artifact creature in play even with Dress Down in play. CR 614.12 sees Sculpting Steel as just an artifact in play so we do not apply Dress Down’s effect on it.

The Queen

With a Dress Down in play, the following happens:
Emrakul on the stack continues to have its can’t be countered clause.
Emrakul’s cast trigger for Time Walk still triggers.
Emrakul in play loses Flying, Annihilator 6 and protection from coloured spells.
Emrakul’s put into graveyard from anywhere shuffle effect still triggers.

Verified by: Steven Zwanger, Monsuporn Lauhaphand & Gerard Trpin
Scenarios contributed by: Kenji Chong, , Russell Lee ; Tay Yuan Xiang
Credits: Nathan Long’s Morph Rules Problems – Face-down in a Face-up World

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