"Well, now there’s a mod for that."
The following is unofficial/fan-made content.
- For the custom SE enemies, see Alesan's Enemies.
Alesan99
Alesan99's Entities is a mod of Mari0 1.6 made by Alesan99. It was first released on September 8, 2013 as just a small mod with very few additions but as time went by it has now evolved into what many of the Stabyourself community call the best Mari0 mod. It is one of the only mods still being supported to this day.
This mod adds a variety of entities, over 200 of them! But despite the name, the mod adds many features besides new entities including more tile properties, custom enemy properties and even better online multiplayer (If you're playing with only a few people with good wifi, it will still suffer when there are 10 people from all around the world, with different connections speeds and devices)

Latest Update[]
The latest update is V13E and it adds:
Mobile/PC
- New enemy properties
- Other misc fixes and improvments.
Future Updates[]
- V13.1 - On/Off Tracks + several new enemy properties.
Other entities[]
Everything else[]
- Customize-able map assets! (Text, Graphics, Sounds, Backgrounds, Music and More!)
- More tile properties! (More slope types, Ice, Vine and Music note)
- Daily Challenges! (Next to DLC)
- Online Mappacks! (Download from DLC)
- Custom Entities and Enemies! (SE Enemy compatible and over 100 new properties to make better ones)
- Custom Power Ups! (Cloud Flower for example)
- Animated Backgrounds!
- Online Multiplayer!
- https://www.youtube.com/watch?v=obfslB7rTYY&t=3s - Port Forwarding
- https://www.youtube.com/watch?v=6D-b1LDWG4c - Hamachi
- 6 Physics Options! (Mario Maker, SMB2-j and More!)
- SE Animations! (As well as around 100 more exclusive to AE)
- Extra level options! (Auto-scrolling [with speeds], Lights out, Low gravity)
- Rising water (Clear Water, Water, Lava, Poison, quicksand)
- New default mappack, Alesan's Entities Mappack.
- Tooltips
- and More!