I've compiled 4 bugs that I've found with the new Mega Mario mod
All being when in 'Mega Mode'

The first being that blocks that shouldn't break are broken ( All except bedrock ) 
and while mobs are killed end crystals don't break (another thing that I didn't add in the video is bosses are instantly dead [Ender dragon + Wither], wasn't sure if this a bug or not)

The next being that the eye location for the player model is too high so the player's model is looking just off of the camera
and the camera is also too low (at 3 blocks when it should be ~4)

Next is that the 'size' of the player is still just the 1x2 blocks (the hitbox isn't though), you can easily fall through a single block hole while it looks like you aren't supposed to

Last is that spectators break blocks when in 'Mega Mode' 
(if embed doesn't work https://www.youtube.com/watch?v=tenTO1IC62Y)

Excellent bug finding from our resident Bug.

Excellent 'Bug' Finding, Gordon!