1-Run past the HQ yelling "I stole Ash's Pikachu before you losers did!"
2-Paint the sign of another evil team on one of Team Rocket's walls.
3-Complain about wanting a promotion.
4-Say how much better Teams Aqua, Magma, and Galactic are than TR (Although, in my opinion, that's not true)
5-Tell a Grunt that they got a promotion(When they didn't), and go receive it from Giovanni.
6-Tell them their Zubat will revolt at night.
7-Cut off Jessie's hair.
8-Surround the hideout with Beedrill and Scyther.
9-Steal an Earth Badge from the Viridian Gym.
10-After doing 9, leave a note saying "I didn't need to battle anyone, TR is weak"
11-Cosplay as another evil team and battle other rockets.
12-Dress up as a ghost and run around the hideout.
13-Cosplay as Silver and Tell Giovanni that you love him THEN hug him(and call him dad) front of all the Team Rocket Grunts and Executives(or just bribe Silver and make him do this himself)
If you have any more tell me and I'll add them.