Catch 5 TNT - How does one catch TNT in the first place?
Hatch a pig - I heard this is luck-based, unfortunately..
Create an iron golem - Also this one seems to be purely based on luck
Find the null - What difficulty is it that you have to play in?
100 nutrition to Mr. Blobbo - This achievement is nearly im-possible. The closest I've gotten in my years of playing was 91
1: I believe, but can't exactly remember, if you right-click a thrown block of TNT in the 'Throw the TNT' Microgame then you'll pick up the TNT instead. Can't say for certain though.
2: Each egg thrown has a slim chance of spawning a pig instead of a chicken in the 'Hatch X Eggs' Microgame. Can't remember the exact number, but if luck is on your side you should be able to get it in under 15 - 20 games of MinerWare, considering how many eggs get thrown in that game.
3: Yeh, like the one above, every time you build a snowman in the 'Build a Golem' Microgame there's a small chance it spawns an Iron Golem instead. However this is a much easier chance than the last one as you only build one golem per game. I think I remember during testing we were getting 1 about every 5 games as long as people weren't sabotaging each other.
4: This works in both difficulties. The 'Null' is just an item which looks like a
red circle with a line through it, or a pink and black textured item if the resource pack you have doesn't support the texture. Every time the 'Find the Item' game runs there's a somewhat small chance it'll put the 'Null' in just one of the chests in the game, so you are lucky if you find it. I always find it handy to keep looking in the chests for the 'Null' even if you've spotted the item the game has asked you to find, because if you click on the 'Null' you'll still win, and you get an achievement too!
(Plus there are several different kinds of Null, if you have a second to spare read the full name of the Null to see which you found before clicking it.)
5: The tactic is to just keep running and aim for as much grouped together food as you can, keep your eyes open and never pick up a negative value item. Also don't keep running back and forth to Mr. Blobbo, just make sure you give yourself enough time to feed him all in one go at the end.