In Plain Sight/Funny

Mary: You're...verbally impotent.
Marshall: [looks pained] I swear this has never happened to me before.

In a season 4 episode, Mary gets impatient while her charge admits his love for a long-time flame, who he was set to testify against. She completely skewers the entire "Cannot Spit It Out love reveal" process.
In Season 5's "Drag Me to Hell," Marshall goes undercover as the witness for a sting operation. The thing is, the wit happens to be a Drag Queen who keeps performing at clubs despite the threat to his life. Hilarity Ensues as Marshall the Recursive Crossdresser sings a rather impressive rendition of "I Will Survive." Then the Big Bad shows up...