To set the tone, my husband wore a lab coat and impersonated Dr. Doofenshmirtz the whole time, he does a great version of that guy, and my son wore a special T shirt with a giant 6 made of Phineas and Ferb fabric appliqued to the front that I had custom made on Etsy.  I also purchased the sound track to the cartoon which I made great use of in all the games as, you will see below.

Since it is a permanent summer vacation in the Tri-State Area where the two boys live, we started by making backpacks. I bought one white string backpack for each kid and laid them out on a table with fabric markers for decorating.  I also had the kids put their names on them and wear them because I handed out prizes for the activities which they could stash away in there.

Then we moved on to fun Phineas and Ferb themed games:

1. Where's Perry  Scavenger Hunt:  If you ever watch the show, Phineas always asks "Where's Perry?"  at the start of each show, which gave me the idea.

I bought some Phineas and Ferb tattoos and hid them all around my apartment and let the kids hunt for them.  Everyone who found at least 3 won (which is everyone) got to keep the tatoos as a prize.  While the hunt was on, we played the Perry the Platypus Theme song from the soundtrack.  If you wanted to spend more money you could actually hide little plastic Perrys instead.  The tatoos were easy, inexpensive, easy to hide and find - plus kids love them.  If you wanted to you could even get a wet sponge or paper towel and put them on after they found them.

2. "You Are So Busted" Balloon Pop:
Candance lives to bust her brothers -- so we busted balloons in her honor.  Warning - this takes a lot of work to set up -- and it is loud! I blew up 30 latex balloons super tight and stored them in garbage bags till I needed them. When it was time for this activity, I scattered them across the floor and told the kids to pop them by sitting on them.  And if they cleaned the balloon pieces up when they were done they got a package of Phineas and Ferb fruit snacks.  I also played the Busted song off the soundtrack over and over till they were all popped.

3. Phineas and Ferb Rocking Air Guitar Contest:
The show has so much great music in it that we couldn't have a party that didn't include music in some way.  So I did an air guitar 'contest'. I didn't expect this to go over as well as it did -- the kids LOVED it. I purchased super cool blow up guitars (yes - more inflating, maybe you should invest in a pump.) and simply put on the soundtrack and let them go wild playing the guitars.  We changed it up and did some freeze guitar in there, too.  They were seriously rocking and sliding around on the floor, doing their best moves and everyone got to keep the guitar.

4.  Mummy Wrap Race:
There is a song about mummys on the CD and my son told me there was an episode about mummys, too. And kids just love spooky, scary things, so I had the kids pair up and play this classic game.  One kid wrapped the other kid mummy style in white crepe paper streamer -- then that kid had to walk a few feet and return, rip off his mummy stuff and then wrap the other kid up.  Everyone was a winner and got Phineas and Ferb silly bands for a prize. This was a HUGE hit. they all loved it.

I didn't serve pizza at the party but did serve cake and ice cream. 

For the cake, I happened to have a big top cupcake pan, and since I don't think Phineas and Ferb would ever have anything as mundane as a plain old layer cake - I made a big top cupcake.  I also stole a trick from my friend and dyed the batter four different colors and swirled it together so the finished cupcake looked marbled and cool. Then using a pastry bag with a large star tip I piped orange frosting onto the top, added colorful sprinkles and it looked like a giant cupcake.  It was awesome but you could also just buy a giant cupcake at a bakery if this idea scares you.

For the ice cream I set up a "Dr. Doofenshmirtz birthday-inator ice cream sundae bar" where I set out a ton of toppings and gave the kids two small scoops of ice cream and let them go to town. I put the sauces and stuff into squirt bottles so they could be kind of like mad scientists while making them. I think there is some reference to ice cream in the show - but mostly my son wanted to make ice cream sundaes at his party so it I made it work.

The one thing I wanted to do but didn't -- mostly because the kids were crazy and a little young, is to create "inators" -- like the Dr. is always doing.  I saved all this recyclable stuff -- cans, plastic bottles, toilet paper rolls, bubble wrap, etc etc. and wanted to put it all out and let the kids create a giant contraption with it.  I think a project like this would be just perfect for older kids who could actually focus while at a birthday party -- which many 5 and 6 years old can't.   I feel like you can't have a Phineas and Ferb party without making something, which is why we did the backpacks at ours.

Tips for an at home party:

I kept it super small - which allowed me to spend money on all the props and prizes - which made it extra fun.

Plan on 1 1/2 hours to do it all. I over estimated and had to throw in hot potato and telephone to fill up the time.

Get friends to help! I had a friend of mine come over to help me with the activities, and since most of the kids didn't know her they listened to her a lot better than they would have me.

If you live in an apartment building -- tell the people who live below you what you are doing and when.  They will appreciate the effort and this makes for good neighbors. Then you are free to make as much noise as you want.  A Phineas and Ferb party shouldn't be quiet.

Set up the ice cream bar in advance.  It is easy.  I put everything in silicone cupcake wrappers and then on a sheet pan and covered it with plastic wrap the day before.  Unless it was perishable.  Also, scoop the ice cream into portions on a sheet pan and slide it into the freezer so you don't have to fuss with the scooping while the kids are screaming for their ice cream.

Put signs on the doors of the rooms you don't want the kids to go into.  They don't have to run of your entire apartment.  I picked this trick up at an adult holiday party where kids were invited.  Works like a charm.

More Birthday Party Ideas in our Birthday Party Guide.