Transforming into Dwarf or Halfling (small races) will allow you to squeeze through the crack in the wall to kid-thieves hideout.
Sorry to say it only disguises you and does not in fact alter your real apparance or size; from the spell "The changes wrought by this spell fail to hold up to physical inspection. For example, if you use this spell to add a hat to your outfit, objects pass through the hat, and anyone who touches it would feel nothing or would feel your head and hair. If you use this spell to appear thinner than you are, the hand of someone who reaches out to touch you would bump into you while it was seemingly still in midair."
https://www.dndbeyond.com/spells/disguise-self
