Can I use the Dimension Door spell to teleport onto the back of an ancient green dragon?

Question

The "Climb onto a Larger Creature" action option in the Dungeon Master's Guide (p. 271) says:

If one creature wants to jump onto another creature, it can do so by grappling. [...]

As an alternative, a suitably large opponent can be treated as terrain for the purpose of jumping onto its back or clinging to a limb. After making any ability checks necessary to get into position and onto the larger creature, the smaller creature uses its action to make a Strength (Athletics) or Dexterity (Acrobatics) check contested by the target’s Dexterity (Acrobatics) check. If it wins the contest, the smaller creature successfully moves into the target creature’s space and clings to its body.

I think that dimension door or perhaps misty step would allow me to bypass the opposed Athletics/Acrobatics vs. Acrobatics check to place myself onto its back.

From there, it can use its action to shake me off (or whatever the DM can come up with). but mostly I'm curious about rulings for teleporting onto a creature. Certainly the place it is is occupied, but I'm not trying to land there.

Can I use the dimension door spell to teleport onto the back of, say, an ancient green dragon?

Answer 1

Yes, but it doesn't bypass checks to remain on the dragon.

First, let's examine dimension door.

Dimension Door

You teleport yourself from your current location to any other spot within range. You arrive at exactly the spot desired. It can be a place you can see, one you can visualize, or one you can describe by stating distance and direction, such as 200 feet straight downward or upward to the northwest at a 45-degree angle, 300 feet.

Getting to the dragon isn't a problem. You could visualize the back of the dragon, or you could teleport a few feet above it.

However this doesn't bypass the dex/strength checks (DMG p. 271):

After making any ability checks necessary to get into position and onto the larger creature, the smaller creature uses its action to make a Strength (Athletics) or Dexterity (Acrobatics) check contested by the target's Dexterity (Acrobatics) check.

This isn't without issue, though.

After you dimension door onto the dragon, you still make a check to remain on there. This check requires an action, which raises the problem of the action being consumed in order to cast dimension door, leaving no action to cling onto the creature.

There are a few options to get around this.

1. Quickened Spell(Metamagic)

Allows you to cast dimension door as a bonus action, leaving you with an action to cling to the dragon. This is simplest option. All it requires is two levels of sorcerer and burning 2 sorcery points.

2. Action Surge

This option requires at least two levels in Fighter, costing you some levels in spell casting classes. Less of an issue if not a main spell caster, such as an Arcane Trickster Rogue. It also only can be used once per rest.

3. DM Fiat

This is basically ignoring the problem but still belongs here for the sake of completion. Your DM could rule that instead of clinging onto the dragon with an action, you could balance your self on the dragon with a check.