Despite only being in the show since Season 3 (though we did get a small glimpse of her in the dying moments of Season 2), there's no doubt that Michonne is one of the most important characters in The Walking Dead.
Though Michonne has spent time with all members of the group during her time in the series, there's no doubt that she's closest to the Grimes family and, in fact, her actions in the mid-season premiere pretty much proved she's basically a Grimes herself.
Following Jessie and Sam's horrible deaths, Rick was immediately confronted with a crazed, gun-toting Ron. Luckily for Rick, his right hand woman Michonne had his back, immediately jumping to skewer a kid in order to keep him safe. Unfortunately, poor Carl was shot in the process – something which Michonne was the first to notice:
What followed was a panicked Rick carrying Carl through the herd of walkers to the infirmary. However, it was Michonne who really risked it all, running ahead of Rick and taking down any walker in her path. Check out the utter anguish in her face as she races to get her adopted son to safety:
As they reach the infirmary, Rick can't even explain Carl's injuries to Denise, leaving Michonne to tell her it was a close-range handgun wound, and also allowing her to remove his walker-guise poncho before he races back outside to take on the herd.
Michonne, however, keeps a relatively level head and remains with Carl, holding him steady as Denise stitches his wound. Only after Denise is finished stitching does Michonne allow herself to kiss Carl on the forehead, and race outside to assist Rick with total walker annihilation.
Without Michonne there's no doubt that either Rick and Carl wouldn't have made it to the infirmary – or perhaps Rick himself would have been killed by Ron.
Michonne's tight relationship with the Grimes family goes back to her initial arrival at the prison in episode 7 of Season 3, when Rick and Carl protected her from walkers and brought her inside the prison fences.
Further into Season 3, in episode 12 her relationship with Carl really grew when she helped him recover a family photo for baby Judith, (as well as taking a papier-maché cat as a present for herself).
In Season 4 she bonds with Carl over comic books, and also spends some time with Judith, who reminds her of her own child, Andre, who died early on in the apocalypse. Following the destruction of the prison, Michonne is separated from Carl and Rick, though eventually finds them again, much to the panic, and then amusement, of Rick.
Despite being homeless and separated from the group, Michonne and Carl keep each other's spirits up throughout Season 4 (even if it does cost Michonne half a Big Cat chocolate bar).
The end of Season 4 may have solidified Michonne's relationship with the Grimeses the most. In the final episode, Michonne and Carl are very nearly kidnapped and raped by a group named the Claimers, however Rick saves them from this fate by ripping out the neck of one of the group with his bare teeth. Though Rick saves Carl by doing so, the moment traumatizes Carl, and it's Michonne who he confides in. In return, Michonne reveals to Carl how her son died, and that after cutting herself off emotionally he, Rick, and Andrea were the people who saved her.
Despite Rick and Michonne not being a romantic couple, there's no doubt that these two make an unbreakable pair, and in the process Michonne has become an amazing adoptive mom to both Carl and Judith.
'The Walking Dead' returns with episode 10 will air on AMC on Sunday, February 21st.