Stampy lampshades this in Episode 678, 'Dangerous Day'. note That's 28% of the titles and not including ones which are only partially alliterative. 112 of the titles of the first 400 episodes alone have alliterative titles.

Alliterative Title: Stampy is oddly fond of this.

in Minecraft's equivalent of H-E-double-bent-straws, after dying in 'Unexpected Drama'. note It's is more implied than anything, but the point stands since a then-dead HitTheTarget respawned in the Nether, i.e. Extraterrestrial life? Stampy befriended them once and now they show up every once in a while. The Tooth Fairy? She operates a dentist's office downtown. The Easter Bunny? He drops by every year or so to hold an Easter egg hunt. Santa Claus? He stops by every Christmas and one of his reindeer is one of Stampy's close friends.

All Myths Are True: If you ask about childhood story elements, they seem to be around every corner in the Lovely World.

Alien Episode: Whenever the Lunar Friends are involved in an episode, it automatically turns into this.

Stampy theorizes that the tractor beam of the Lunar Friends' UFO wasn't strong enough to lift them up, which was how they ended up on top of buildings all over the place.

Aliens Steal Cattle: Cows could be found on top of buildings up to the episodes leading up to Episode 110, 'Lunar Friends'.

After the End/ Zombie Apocalypse: One of the scary movies watched in the 2017 Halloween Episode, Block of the Dead, takes place in such a setting.

In Stampy's case, at least, he's using his screen-name and not his real name (though there have been allusions to his real-life name in the series), and this would presumably apply to most of the Helpers as well.

Aerith and Bob: You got names like 'Stampy', 'Veeva Dash', and 'Fizzy', and then ones like 'William'.

Added Alliterative Appeal: Several minigames and shops are named this way.

Abnormal Ammo: The SS Stumpy has snowball cannons, to reflect the Lovely World residents' more peaceful nature.

Minecraft stampys lovely world 1