Tips for some of the achievements.
Tips to Obtain Achievements
Multiplayer: in the ending room below one player goes into the replay door while the other goes into the elevator on the right and wait for a couple of seconds till the achievement pops.
Push It Real Good
Singleplayer lvl104: one stand on the right side of the crate and the other one keep pushing until the achievement pops.
Let Me Go!
Multiplayer: keep pressing A or spacebar to free yourself while the other player holding you.
Multiplayer lvl107: at the beginning of the level, stay in the position below and the left small person let go of the switch. the achievement shall pop.
How to Die Here?
Singleplayer lvl103a: stay in the position below and press RT or Q. remember the gap shall be too narrow to fit the bigger guy so as to kill him.
Multiplayer: one person has 75 coins and the other one has zero in the settling room.
Multiplayer: those silver moving little spheres which you have to touch multiple times to earn the final coins, let one person touch it all except for the last time when it turns fully golden, and now the other player touches it to credit those coins, the achievement shall pop for the person who finally ate it.