At the end of the episode, Perry and Della walk into the darkened outer office. Perry turns on a lamp on the desk behind them and both their shadows appear - on the wall, also behind them.
(At about 48 mins) When Perry is mixing up the fish-medicine mix, the fish tank on his desk is noticeably empty. In the subsequent shot, there is a (very artificial-looking) goldfish in it at one end.
When Hamilton Burger is questioning the "officer", the shadow of the microphone boom can be seen behind the witness.
Perry tests the fish formula on some sick fish using Metcalf's analysis and the compound doesn't work to revive them. If Perry wanted to do a test or double check Metcalf's analysis all he had to do was ask his client Wyatt for the real formula or have Wyatt review the chemical analysis to see if it was complete and correct. Executing a test with the wrong formula was unnecessary.