I know that the basic bricks of LEGO and Megabloks fit together, but was wondering if other elements do too.
- Rods (Ones Minifigures can hold, not Technic)
- Right angle (such as Erling)
- Duplo bricks
My mother in law thought a set of MegaBlok duplo sized sets would be a great present, and while there are some fun elements in the set, overall the real Duplos are better quality, to the point we decided to sort out the sets and keep the brands separated. At first we had them mixed together, but the MegaBlok ones seem to be more flexible (perhaps thinner brick walls?) and not stay together quite as tightly. (For that matter, the Tyco bricks didn't stay together as well either...)
One of the most jarring differences, aside from quality, is the people figures. The legs on duplo people are designed such that they can be standing or seated on top of a brick. Megablok people do not have gaps on the back of their legs for seating them on blocks, they can only stand. For this reason, all the Megablock vehicles and benches and whatnot have flat bottoms on the part where the characters sit. So Megablok characters don't "play well" in real Duplo brand vehicles, chairs, and so forth. And the duplo figures don't play well on the swings and so forth that are designed for Megablok characters.
Also, while Duplos are usually for ages 1.5+, an equivalent Megablok set often is 3+ because it contains half-bricks and half-height half bricks, teeny tiny birds and squirrels, and so forth that are all choking hazards, so it was a lot more work to figure out which pieces need to be pulled out of the set to make sure baby brother doesn't choke on the pieces.
Additionally, while newer legos for older kids do sometimes contain sticker kits (grumble), usually the Duplo products have the designs printed directly on the bricks, so they are fully immersion washable if they get spit up on by a younger sibling and safe to take in the tub at bath time. The megablok ones? Every single patterned element except people characters require a sticker you have to apply yourself. You can't wash them or take them in the bathtub without ruining the stickers.
I can't actually offer any thoughts regarding anything but actual bricks, as the first - and only - megabloks purchase I ever made only contained bricks. While my experience with megablocks is limited, I feel confident in offering this advice: Don't do it.
My motivation for "playing" with Lego-style blocks at age 29 is probably pretty unique - I use them to make floor toys for my sugar gliders to play on (meaning I have no interest in figures and many other elements). For my first block purchase, I bought Megablocks because they were cheaper and I foolishly assumed they'd get the job done... let's just say, lesson learned! I tried to build a simple "house" that was perhaps 5''x5'' and by the time I'd built 3-4 layers of overlapping 2x4 blocks, my creation was falling apart faster than I could build it. They didn't stick together at ALL - the quality was ridiculously poor. Suffice it to say, I returned the bricks for a refund.
Since then, I've stuck to Lego Duplo blocks and not only can I actually build things without them falling apart, my creations easily withstand a lot of jostling. I can only assume that mixing megabloks with Duplo blocks would weaken the integrity of your Duplo creations.
The problem is that while in general MegaBloks bricks fit with LEGO bricks, the quality control on the MB bricks seems to be much lower*, so the bricks/studs and holes are not always the same size.
As an example, I recently acquired a MB HALO Covenant Banshee ship for my son, and can safely show that:
The holes in studs do not readily accept rods (in this case a "wand" element from a Harry Potter set, but identical to the lightsaber pieces, etc.) - they are generally too small, however I could just force it into the front of the "hollow frying pan" type piece that Harry's holding. Conversely the handle is thinner than the wand, so it fits into the hollow MB studs fairly well, but is very loose in the LEGO cone.
With Erling bricks your mileage may vary but shound be ok, however you'd be better off with the newer 1x1 brick with knob(s), as then there's no ridge to fit within.
Plates and Tiles seem to fit fairly well - although generally the grip will be looser if you put LEGO elements on top of MB ones - the studs seem slightly smaller.
DUPLO Bricks seem to fit as well as they do with LEGO bricks:
*I state that the quality control seems to be lower as in this set for example, there are supposed to be 4 1x1 Round Plates (you can just see a transparent blue one behind Harry). Of the 10 or 12 that were supplied(!), none of them were tight enough to stay on the angular brick you can see on the wing edge (the one that just about stays on the other side falls off this one).