There’s a “Little Miss Sunshine” reunion on the horizon, as Steve Carell and Toni Collette are joining the cast of Jim Rash and Nat Faxon’s directorial debut “The Way, Way Back.”Sam Rockwell, Allison Janney and Annasophia Robb were already attached to star in the indie, which follows a teen boy who struggles to find himself as he comes to terms with his unattentive mother and cheating stepfather during summer vacation. Collette will play the boy’s mother, while Carell will play the protag’s stepdad, who likes to drink, do drugs and carouse with other women. Kevin Walsh is producing through his Walsh Co. banner, and production is skedded to start this summer. Faxon and Rash’s script appeared on the 2010 Black List. Scribes recently sold an action-comedy pitch to Indian Paintbrush that Walsh is producing, with Kristen Wiig attached to star. Carell, who recently wrapped New Line’s magician comedy “The Incredible Burt Wonderstone,” will next be seen in “Seeking a Friend for the End of the World” and Sony’s “Hope Springs.” He’s also skedded to star in Charlie Kaufman’s musical satire “Frank or Francis” and Bennett Miller’s “Foxcatcher.” Collette recently starred in DreamWorks’ “Fright Night” and will next be seen in the indie “Jesus Henry Christ.” Thesp will soon begin filming Sacha Gervasi’s “Hitchcock.” WME reps Collette and Carell, who is also repped by Media Four. Additionally, Collette is repped by Shanahan Management and attorney Deborah Klein.