Charlie Sheen's son Bob got his hands dirty at the park yesterday ... and he wanted to show us just how messy he was!

The cutie (who looks like his daddy's mini-me), played on his tricycle and dug in the gravel pathway while his grandparents looked on. Fortunately his new guardians are keeping him and his twin brother Max away from their parents' drama. Charlie's out of work now that Ashton Kutcher has been announced as his official replacement on Two and a Half Men and mom Brooke is working to maintain her sobriety.