Justin Timberlake glasses beard singer jim hensen shrek 4 Justin Timberlake glasses beard singer jim hensen shrek 4 Let's hope Jessica Biel isn't the jealous type.

Yesterday Justin headed to Jim Henson studios to start his voice work as Artie in Shrek Forever After. It's not clear whether or not he'll actually be inside the sound booth with his ex-girlfriend, who plays Princess Fiona, but since Jess and Justin have been on the rocks as of late, I know I certainly wouldn't want him getting up close and personal with Cameron Diaz!