Muck in
Definition 1 of 2
Pro Tip 1/3Team Spirit
Used when showing cooperation and support within a group. 
During the fundraiser, everyone mucked in to make it a success.
Pro Tip 2/3Casual Use
Typically used in casual or informal situations, not in formal writing. 
Let's all muck in and get the garage cleaned up this weekend.
Pro Tip 3/3Positive Connotation
Carries a positive feeling of camaraderie when used in context. 
When the community garden project started, neighbours mucked in happily.