Cobblers manager Chris Wilder started the ball rolling on loan deadline day with the capture of 22-year-old midfielder Ollie Banks on a deal until the beginning of January.
The Chesterfield man has been described by Wilder as an 'energetic' player who likes to get forward.
Completion of that deal has allowed John Joe O'Toole to join weekend opponents Southend United on loan until 24 January.
He could play against Northampton twice during that period with Wilder explaining that the deal would not have gone through had he not given permission and that Banks would not have arrived otherwise.
The day was also expected to see Ivan Toney complete a club record move to join Wolverhampton Wanderers but, despite the young striker undergoing a medical, the Championship club have opted out of the transfer.
Update: Alex Nicholls has agreed a return to Exeter City for a second loan spell of the season.